Is Rotel RMB-1075 a good match for B&W N804

I have a B&W N804 driven by RMB-1075 primarily being used for HT. I listen to music on my headphones, only just recently have started to listen to music on the 804's. There seems to be little bass & midrange , not sure if it is the rotel, I've even bi-amped but found just a little improvement in the bass & midrange.
What's the rest of your system? The problem may lie elsewhere.
Oppo BDP-103 and Yamaha RX-V650 as the pre.
The Oppo has its own volume control. Try plugging it directly into the amp so that you bypass the Yamaha. You should hear a very big difference.
Home theatre receivers, in general, tend to perform very poorly as preamps. The Yamaha would definitely be a major problem for sure.
Bypassed the Yamaha and plugged the Oppo directly in the Rotel, see a big difference. Overall sound quality is very good, see a gain the midrange but not enough in the bass. Thank you. Which pre-amp (in the $2000 range)would you suggest that can go well with the B&W and Rotel gear that I can use for both music and HT ? How about the Emotiva XMC-1? Or should I look at Parasound P7.
If possible try the Parasound P5. I had one and for the money it just may do the trick.
Since removing the Yamaha didn't solve your bass issue, you've got something else going on.

Assuming you are running the main speakers full range, you should make sure you are not sitting in a bass dip before spending any money.