Amp/Preamps vs. High end AV Receivers

As others have mentioned, upgrading the amp without upgrading the preamp will only get you so far, and upgrading to separates will be pretty expensive.  Given your investment in speakers, if it were me I'd upgrade to a higher level AVR so you upgrade both the amp and preamp in one shot.  Anthem makes relatively high quality AVRs, so I'd look for something like this if it has the features you're looking for.    

https://www.audiogon.com/listings/lis974j9-anthem-710-receiver-receivers

If you want to go further than that, I'd do a Marantz prepro with maybe Rotel or Classe multichannel amps, but it will cost a lot more and you'll need to add good interconnects.  FWIW, and best of luck. 

Yup....do not underestimate the important role of a preamp or pre pro. This is one element that is often times overlooked by many.

If you can swing around $5500 or so I would recommend the Classe Sigma SSP preamp processor, which is optimized for stereo, with the matching Classe Sigma Amp5 five channel amp. However, like I said before the Sigma Amp5 is a class D design amplifier which is good for surrounds (HT) but isn’t my preferred choice for music. But the Sigma SSP is an excellent sounding pre pro especially for stereo music playbacks. This combo can be had in used markets for around $5500 to $6k altogether both used plus analog interconnect cables to connect between the two. Do not skimp on cables.
Classe also makes class AB amps called the Delta series which are excellent for both music and HT but they are way more expensive than the Classe Sigma Amp5 or any Classe Sigma series amps (class D).

Or you can pair the Classe Sigma SSP pre pro with the Rotel RMB-1585 five channel amp, which is class AB design amplifier. Actually I have heard this combo before at someone’s house and they sounded very good together especially on B&W speakers. The Rotel RMB-1585 amp will pair really well with your B&W CM8 and they will sound great together.
The Rotel RMB-1585 retails for $3k new and sometimes you can find a used one for around $2k ish. It is a very good amplifier very refined sounding and very musical especially for the money. The Classe Sigma Amp5 (class D) is more suitable for surround movies or HT than the Rotel but the Rotel RMB-1585 is more inviting and engaging for music.

As always, appreciate the inputs and let me take this forward.