Sanity check on new system?

How do you control the volume?

I haven't heard the 803s, but from everything I've read, it seems they perform best with high power. My KT88 Cayin amp was modeled after the MC275 and has similar power. I don't think I'd want to pair it with B&W 803s, but if you already own the 275, won't hurt to try it. 

It's best if you can manage to audition gear somewhere, especially speakers, as they will have the greatest influence on your system's performance. You might discover you don't like B&W.

Mc's can be bright, so can B&W's.

I would listen to the combo first. :) 

Also, when you get it, learn about room acoustics. From floor rugs, to pillows on the floor and thick curtains, all can help your system come up a few notches. A good room acoustically is much more speaker friendly.

Best,

E

Unless your room is tiny, I'd consider something like a JL Fathom 110 sub.