To get the closest to higher end SQ, I would go with Marantz. Denon would be my second option. 80-100W per channel will suffice. Marantz SQ is top notch, and I highly recommend it, if you want to get the most from your B&W's. I recommend Marantz SR-5002, it also has multi-zone capability, bi-amp option, and the needed HT features (HDMI 1.3, DTS HD, DD Plus, etc.). This is a very musical receiver that does a great job for HT also.
If you want more power for your second zone, or keep 7.1 in the main room, just connect an amp to the multi-zone pre-outs.