It is a truth universally acknowledged, that a single home theater junkie in possession of a good AV receiver must be in want of AV separates. Universally acknowledged, but is it universally true? As with most things in the audio world, no. But it isn't a simple "no."
Confused yet? If so, that's fitting, because the choice between AV receivers and AV separates is a complicated one. Anyone who tells you otherwise without knowing the details of your listening room, speaker system, and general listening proclivities is merely relying on conventional wisdom ... and outdated conventional wisdom at that. So, let's tear into some of that conventional wisdom. But before we do, let's define a few terms.
What, exactly, do we mean when we say "AV receivers" and "AV separates"?
For our purposes, let's define an AV receiver as any device that combines video switching, multichannel audio processing, and amplification in one chassis. That includes products that eschew the "r" word, like Rotel's RAP-1580 Surround Amplified Processor, which sets itself apart by excluding the radio tuner that originally gave the receiver its name. Add a display, a speaker system, and some sources to the RAP-1580, though, and you've got yourself a fully functional home theater, so we're lumping it into the receiver category.
A system built around AV separates, by contrast, includes one box that performs the video switching and sound processing duties and another (or perhaps several others) that handle amplification duties. This might mean a single five-channel amp for a 5.1-channel home theater; a 7- , 8-, or 11-channel amp for more expansive systems; individual mono-block (one-channel) amps for every speaker (or sometimes even every driver) in the system; or some form of mix-and-matching from the above possibilities.
Right off the bat, with no more information than that, you can already see pros and cons of each approach. A receiver delivers simpler connectivity--in that you don't need to string cables between a preamp and amplifiers--and it generally takes up much less space than separates. Running a preamp with separate amps, though, gives you much more in the way of design flexibility and scalability, as well as your choice of amplifier topology (Class A, AB, D, G, H, etc.) and--here's the kicker for most people--more sheer power output. After all, a really beefy AV receiver might give you 100 watts of power per channel (at least on paper), whereas something like Anthem's M1 mono block cranks out a face-ripping 1,000 watts of juice, one speaker at a time.
Going further, most dedicated amp manufacturers are much more conservative in their power ratings, giving you a truer picture of how much power you're getting per channel with all channels driven at the same time. Receiver manufacturers often rate their products' power with two or even one channel driven, since their wimpy power supplies start to struggle when asked to deliver much more than that at once. And even receivers that report the same power output might not actually deliver the same output. I've reviewed so-called 100-watt-per-channel receivers that nearly peeled the skin off my cranium without breaking a sweat, and others with nearly identical specs on paper that completely crapped out when trying to deliver the same scene at the same SPL.
Making it all the more confusing is the fact that, sometimes, receiver manufacturers rate their output with a six-ohm load instead of the more standard eight-ohm load, at least until you dig into the fine print. That "160 watt" receiver you're eying may only deliver something like 50 clean watts of power per channel once you get it into an actual home theater setting.
That doesn't sound like nearly enough power, does it? Here's the thing, though: it might be. If you're not familiar with the relationship between amplifier output, speaker impedance, sensitivity, and so forth, I would encourage you to pause for a minute and visit our older guide to Picking the Right Amp for Your Speakers (or Vice Versa).
If you don't have time for all that, the TL;DR version is this: depending on how sensitive your speakers are (in other words, how loudly they play when measured from one meter away with a one-watt signal), how far you sit from them, how big your room is, how absorptive your room materials are, and the load those speakers place on your amplifiers, the power provided by your average $700 receiver may be all you ever need. Factor in hybrid powered speakers like GoldenEar's Triton Reference and Paradigm's Persona 9H, which feature their own built-in amplifiers for low- and ultra-low frequencies, and you need even less power than you think. My own Triton Ones could just about be driven like a rented mule by a 9V battery. (I'm making hyperbole here, people. Please don't try to drive your speakers with DC power.)
So, what I'm saying is that separates are a scam, right? Of course that's not what I'm saying. While it may be true that most users and most speakers in most rooms are probably adequately driven by the average AV receiver, has mere adequacy ever been the driving principle in our hobby? There may also be any number of legitimate reasons for needing (or just plain wanting) more power than an AV receiver delivers. Say, for example, that you really have your heart set on (or already own) a set of Dali Euphonia speakers. While these may not be the most difficult-to-drive speakers in the world, they do have a nominal impedance of four ohms, which means that they're going to draw a lot more current from your amps than a nominal eight-ohm speaker. (Again, all of the math for this is detailed here.)
While a good number of today's receivers claim to be able to handle a four-ohm load, most do so by simply limiting the voltage when you engage the four-ohm selector switch to keep your AV rack from turning into a kiln. While there are receivers out there that claim to offer high current in order to drive four-ohm loads, it isn't always easy to determine if this is a legit claim from manufacturer to manufacturer. What I'm saying here is that, if you have a particularly hard-to-drive or exotic speaker system, you may actually need beefier amps than an AV receiver offers.
But let's get off the issue of "need" for a minute and talk about simple preference. I will always, always, always use a separate preamp and amplifier in my reference home theater system whether I "need" to or not, for one simple reason: I absolutely adore my Anthem A5 amplifier. I love its sound. I love its reliability. I love the fact that I know, without question, that it can drive pretty much any speaker system I throw at it. It's been rocking and rolling with me for over eight years now, and I expect it to keep working for many, many more. In fact, aside from my speaker cables, it's the only component in my system that hasn't changed in the past eight years. I upgrade processors every so often to gain the latest in connectivity and features, but that A5 amp never needs replacing. I might augment it with an old B&K amp when I need to review at Atmos system, but that's it. Simply put, a good amp can last for years and years and more years, making it a heck of an investment (both emotionally and financially).
As I hinted at above, the A5 could be considered overkill with the speaker system I have (built on GoldenEar's Triton One towers). However, what you call overkill, I call headroom. No matter how loudly I crank that system, I know for a fact that I have plenty of extra, ultra-clean amplification to spare. So, if I do happen to blow a driver, at least I know that amplifier clipping isn't to blame.
Another thing to consider is features--although this isn't as important a consideration as it used to be. Even just a few years ago, the average AV preamp was at least a year (if not much more) behind the average receiver in terms of connectivity and decoding. These days, though, preamp manufacturers are doing a pretty good job of either keeping up with the latest in HDMI standards and surround formats or at least offering modular upgrade paths.
That said, AV receivers (at least those from the big-box manufacturers) are generally cranked out at a rate of a new model number every year, whereas your favorite high-end company might only introduce a new preamp once per presidential election cycle. If the bleeding edge is what you're chasing, it's a lot more likely to roll up on your local store shelf in the form of a receiver.
AV receiver manufacturers also benefit from economy of scale, which makes it easier for them to strike deals with streaming music service providers like Spotify, Pandora, and TIDAL--and to pay the often-exorbitant licensing fees to format-establishers like Apple (for AirPlay, in case it wasn't obvious). If having that type of functionality built into your system tickles your boat, you might find the general lack thereof in preamps a bit disappointing. But hey, consider this: just as there are advantages to having your amps and processing in separate chassis, there are also benefits to having your music sources coming from a separate (and easily replaceable/upgradeable) box.
"But what about sheer sound quality?" I hear you asking. (If you'll excuse me, I'm going to go ahead and pick out my own crucifix and nails before I answer this one...) In my years of experience reviewing preamps, amps, and receivers, I've found that there's no universal fidelity advantage to using separates over a good receiver. Notice, again, that I said "universal." It's true, mind you, that most preamps are built with better components than most receivers, and that makes a difference. But draw a Venn diagram of sheer sound quality, and there's a lot of overlap between AVRs and separates. Not to put too fine a point on it, but Arcam's AVR850 smokes most separates systems I've reviewed when it comes to detail, transparency, and dynamics. But I will say this: it's easier to design a reference-sounding preamp than it is a reference-sounding receiver, simply because the preamp designer doesn't have to worry about all the interference from massive power supplies, nor all the heat generated by cramming amps into the same chassis as your sensitive preamp componentry.
If you're having a hard time deciding between an AV receiver and AV separates, the major pros and cons of each can best be summed up as follows:
• Pros: They take up less space; they are easier to connect; they are generally a better value; they are probably more feature-packed (although that delta is shrinking more and more every year); they probably have enough power to drive most speaker systems in most rooms for most people.
• Cons: They will likely struggle to drive more exotic speakers; they might not provide enough clean power for your system, depending on room size; they might not offer the same level of performance as a good preamp; they will likely boast rated specs that have zero correlation to actual performance.
• Pros: They have much more design flexibility and modularity; they likely have much more power, but definitely more clean power; they offer better support for difficult-to-drive speaker systems; in general, they have better design and possibly better sound quality.
• Cons: They take up much more space; they can be pricey; they are more cumbersome to connect; they are possibly limited in terms of features (especially wireless connectivity and music streaming); they may deliver way more power than you'll ever need.
So, for a guide that began with a supposed universal truth, it's pretty ironic that we've reached a conclusion in which there are no universal truths. Or at least no easy answers. But keep in mind the last part of that ripped-off paraphrase I began with: you may not need AV separates, but our hobby is generally driven more by want than need. Do you simply desire a preamp and stack of mono blocks for no good, practical reason other than your own peace of mind? That's totally valid. AV separates may not be quantifiably superior to AV receivers in every respect, but they have a reputation for being so for good reason. With separates, there are no limitations. Or, to be more precise, there are far fewer limitations than there are with AV receivers.
However, if space or budget constraints keep you from going the separate preamp-and-power-amp route, don't let anyone tell you that you're doing home theater wrong. Pick the right receiver and speakers for your room, and it's highly likely that the only thing you're missing out on is bragging rights.
Of course, there's always the option to buy a receiver with preamp outputs and add external amplification down the road as your needs and/or budget increase. Or you can get a kick-ass stereo preamp and amplifier with home theater bypass and add a receiver to extend your stereo speaker system into full-fledge surround sound. But both of those topics require lengthy diatribes in and of themselves.