Amp/Preamps vs. High end AV Receivers

@atmasphere

I have no doubt that even modest speakers would benefit from high end electronics and cablings but some of the posters here earlier suggested the Gryphon Diablo integrated and some suggested Vitus Audio these are $20k+ worth of integrated amps and wouldn’t make any sense to pair them with the B&W CM8 unless if the OP is willing to upgrade his speakers. Besides the OP already stated that he wasn’t willing to pay a lot of money upgrading his electronics. He just needs something better than his Onkyo AV receiver.
And the Rotel RAP-1580 av receiver will be a big step up performance wise from what he has now.

Good qualittle AV separates will of course be better than AV receivers but will cost way more than AV receivers and if the OP doesn’t have budget constraint and yes indeed good quality AV separates will be perfect choice.
However, the Rotel RAP-1580 av receiver will most likely outperform entry level AV sepaeates. While the Rotel RAP-1580 isn’t exactly cheap at $3800 but its audio performance is very good and will sound really good on his B&W CM8 speaker system. I’ve heard this RAP-1580 paired with the new B&W 702 S2 speaker surround system as well as the B&W 804 D3 speaker surround system and I must say that this RAP-1580 beast drove the speakers with ease and sounded quite good especially coming from an AV receiver.

In regards to your comment that there’s always compromise in sound quality with integrated amps, I partially agree with you but really good design high end integrated amps are excellent sounding and there’s no compromise made.
But then of course when you compare them to their own stereo separate counterparts the separates will be better.

In my master bedroom setup I have the Dan D’Agostino Momentum stereo analog linestage integrated amp paired with the Wilson Audio Duette series 2 standmount speakers and they sounded excellent and outperforms many lower end stereo separates. And in my regular smaller sized bedroom I have the Naim Uniti Nova paired with the B&W 805 D3 standmount speakers and they sounded very good. Naim Uniti Nova is an all-in-one box solution streamer/DAC/integrated amp all in a single chassis. Very musical sounding unit for what it is.

However I do have very high end stereo separates (linestage preamp + monoblock amps) in my main reference two channel setup listening room.
I also have very high end AV separates in my dedicated home theater room.

@caphill I personally will not invest in a $4k receiver (i.e both AV processor and amp). And specially when there are no measurements for the amp section of the receiver. Why even bother. No one really know what they are getting. 

You are right it is pointless to consider $20k worth of electronics for B&W CM8. And I would venture and say considering one unit at $4k is also pointless.

One can get great amps for far less than $4k. And once you have a good amp one is free to upgrade AVR/Processor every few years. 

My Marantz SR7005 is not at all close to dedicated AMPs I have, even with really modest speakers i.e Paradigm Studio 40v3.

Unless there is space constraint or usability constraint an expensive AVR is just a giant waste of $$, buy an used last gen AVR for 30% of its cost if one must, IMHO. Good amps are keepers!. Pick a flavor tube class A / SS class A / AB / D/ G/ H and sticking with it, they are better value for the $$ over long term and quite a satisfying musical option.

I always like to get a mid level AVR that has analog pre-outs for plenty of channels, then add an separate power amp.  In the OP's case, that could be a 5-channel amp.  It will, however, cost some money for decent interconnects.  Like some others, I cannot see paying $4K for a high end AVR like that Rotel.  You can get a Denon AVR-X6400 for $1,500, and it has plenty of pre-outs.   Add an Emotiva A-5175 for $799, and you are up to $2,300.

Running a similar type setup.  Started upgrading a couple years ago to bring up the sound quality after a downsizing move created the need to compromise from a dedicated room which had 2 Bryston 4B SST amps and ML speakers.  I run a Denon x4300h in 7.1, Magnepan MMG, REL sub, NHT super 0 surrounds.  The Maggies needed more power so I built the Hypex NC400 amps.  Immediate improvement- dark, controlled, no heat in cabinet.  When I use HT mode all is great.  When I switch to vinyl (Rega P3 with Nag 110 cartridge and Parks Puffin pre), Spotify or CD's I put the receiver in pure direct mode and call it a day.  In my little world I couldn't be happier.  

I had an AVR but then went the separates route.  The overall sound is much better, but I don't need to rehash what others have said.  

I got a used 5 channel amp, and added it as an outboard amplifier.  The AVR has line level outputs, and I connected those to the amp.  The advantage of this type of setup is that you can use a cheaper AVR without much power, and you can use the separate amp to power  your speakers.  

Then, in my case, I later wanted to upgrade to support 4K video, and I was able to score a $1k Denon AVR on clearance for less than $600.  It has all the software support I could need for up to 9 channels, including Atmos.  And, I can use the built in amps for the Atmos speakers if I decide later to go that way.  

In your shoes, if your AVR has line output, then I would just get a separate amp.  If it does not, and doesn't meet your codec requirements, then you can get a nice amp for under $1k (I paid $600 for an older 150 wpc Adcom 5 channel amp), and a nice (lower power) AVR under $1k.  In the future, you can meet any software changes with a low cost AVR, and connect it to your nice power amp.  

This option is way better to me than upgrading to a $2k AVR because when you want to update the AVR, you also have to pay the cost of the amps... meaning another $2k investment.