actually, I'm running 2 MC275's in mono for each B&W 805D's.
Well that's a little more information, but not as much as I was hoping for. If you have your amps bridged, you have more than enough power, and more than enough damping, to get loud, tight bass out of your 805's.
Are your amps located right next to each speaker, using short speaker cables? What brand/model cables are they.