I see there is slight growing trend to multi channel amps for HT. I see that the front 3 channels are higher watts and lower watts for the side, rear, and overheat channels. Does anyone agree with this new trend? I do understand that the front 3 are by far the most important, but are the extra watts an issue. Will the extra headroom overcome the side and rear effects??
Right now I am running 400 watts all around
In my system, I’m using a 3-channel amplifier (Bryston 6B SST2) for the front, center and left speakers (Revel Ultima Studio and Voice). Previously on the same speakers I used a 6-channel Bel Canto bridged to 3. I feel it’s important to have as seamless a match across the front channels as possible/affordable. The Bryston is 300W/channel and between that and my Ultima Sub30, it seemed like my house was about to collapse around me when I watched Blade Runner 2049. 
I’m using a Bel Canto S300 making 150 W for my surround speakers (Revel Ultima Embrace) and never noticed any sense of strain or distortion. There may be multi-channel recordings that engage the surround channels just as much as the front 3 that could stress the amp, but I’ve never experienced that.
Recap: front channels: as same as possible; surround: match tonal balance in speakers, but don’t sweat a slightly less powerful and/or different make of amp
Chris V
Sort of rambling here:
I was happy with my SimAudio 7ch amp (200W /channel @ 8ohms, 400W / channel at 4 ohms) and for (some) music you want equally capable speakers in the back as the front (especially for immersive (highly produced) music.) Still when I went to three 700W mono blocks for the front and a similar stereo amp for the rears the difference was palpable - the bass was firmer and more controlled and (somewhat to my surprise) the detail, clarity and finesse of the highs was better too.
To your question: the music itself sets the overall balance and as long as each speakers can handle its part everything will be fine. Most video related material has much lower demands on the rear (and height) channels so if you exclusively do video, it may be nice to not pay for something you’ll never use. I do have a significant number of multichannel SACDs that have similar levels in the rears as the fronts - but if all of the amps/speakers were going full tilt I’d be in pain…
I certainly agree with the concept of using lower-power amps for surround and ceiling (‘S&C’) speakers. Within the last couple years, for S&C speakers I’ve used 150W-(all into 8) channels of Butler TDB 5150s, 100W channels of an Outlaw 7100, and 80W channels of two Emotiva A700s. I have found that ceiling speakers require more power than surrounds–at least the way I have them level-set–and the Emotivas do just finely. I’ve never noticed ANY amp clipping driving S&C speakers, and I’ve never noticed ANY sound-quality differences among the MANY amps I’ve used for S&C speakers over the decades. FWIW, I also don’t feel the need to ‘match’ the SQ of S&C speakers to that of the main speakers, and I’m quite pleased with the overall performance of my many B6s, some purchased (new) for as little as $200 per pair.
Currently I’m using BHK 300 monoamps for main-left and -right (and LOVING them!) driving the 86dB-insensitive Quad '2905s and two Emotiva A700s (totaling 14 channels, some not used) driving the 10 S&C speakers, those being 87dB-insensitive ELAC B6s.
FWIW, I also use MUCH-less-expensive IC and speakercable for S&C channels.
At the moment I have a 7.1 set up. I use an Emotiva XPR-2 for the left and right fronts ( 600 x 2 ) and a XPR-5 ( 400 X 5 ) for the center, and side and rear surrounds. I also have another XPR-5 ( 400 X 5 ) still boxed for expansion. So I was thinking I’m good with this set up?
With that setup and amplifier power, you’d have to have pretty inefficient speakers not to be able to reach Chicago O’Hare on a Monday morning volume levels. You don’t live in a townhouse, do you? 
LOL, no. Def Tech Mythos ST-L, and Mythos 10 on walls
I went from a 5 channel Mcintosh MC205 200 wpc amp to the Stellar M700’s for the front and sides and a Stellar S300 for the rears. The difference was not subtle. Greatly improved detain and dynamics. The M700 monos are incredibly musically engaging. Much more so than my old Mac which is a very highly regarded amp, BTW.
I don’t agree. Multi-channel amps have been used in HT for as long as I can remember.
I believe the trend he is identifying is multi-channel amps with lower wattage for the side, rear and overhead speakers, higher for the front three - not the mere existence of multi-channel amps.
The multi-channel amps I’m familiar with are equal across all channels in every aspect.
Elk, yes exactly
What if the director wanted a loud boom or scream from the rear of the room, then followed by a crash or explosion in the front channels. Would the higher watts and headroom overshadow the point of such a sound profile? That would be my concern. I could be wrong. Then also take in the math of the effects speakers often being smaller, less efficient, and behind your ears. Not sure less watts and headroom from my amp is wanted under those conditions.?
This occurred to me as well. I do not watch movies (I get bored) but I assume part of the enjoyment of adventure/battle movies is exactly this, big explosions, etc. which amuse and surprise. If these are not reproduced what is the point of a multi-speaker home theater?
Tho I agree that the center (and to a lesser extent the front) speakers almost always need the most power, in a multichannel amp there’s an opportunity for sharing. Almost certainly they will share part of (if not all of) the input power transformer. A natural sharing might be the left rear and left front (etc.): sharing the rectification and top level capacitors. It can be a feature to share some parts of the power supplies between the (probably) lower power outputs and a higher power output. Sound staging is less of a feature in video than in an audio only system (perhaps not even considered during production of the audio for video) so sharing some of the power supply and hence having little less isolation between the channels isn’t the worst thing in the world.
I have spent a lot of time in my HT room both before I have a 5 channel amp in the McIntosh MC205 which has equal power across all of the channels and after I switched to the Stellar combo with M700s for the front 3 channels and S300 for the rears. I think might be surprised at how much less volume is directed to the rears. Not to mention that the S300 can deliver 140 watts into 8 ohms and 300 into 4 ohms which I would think is way more than sufficient for almost any rear channel dynamics. While looking at the meters on my old Mac, I never saw them go over, say, 70% at any given time during a particularly loud section. And I checked. And that was for the front 3 channels, so the rears really don’t move the needle much at all, comparatively speaking. Plus since most HT setups have a sub or subs, that is additional power the amps don’t need to deliver. below, say 80-120 Hz.
Another thing is that any good HT preamp/processor will calibrate according to your amp/speaker combination and proximity to the seating. In my case, my Anthem AVM 60 attenuates the fronts by 3 dB to volume match with the rears in order to volume match. Paul has said that the S300 was designed for such a pairing with the M700. So I think this concern is overblown.
My take on Multichannel separates is get the best amp (s) that your budget allows for the front left & right speaker. For the center channel I’ve never ran them with equal power as the L & R (unless it was with my receiver’s built-in amps). Because of my close distance to my surrounds, I don’t need a ton of power there either. Until I save up for an S300 to power my surrounds, my Sony STR-DN1080’s built in amps will power my center and surrounds while my M700’s power my left & right Series 1 901’s via fixed level true balanced XLR’s out’s that I hacked out of the Sony.
I envy your three M700’s across the front and the S300 for the back.
