Here's what I've got from B&W:
center: CWM Cinema
Front Left & Right: Signature 7NT
Side Left & Right: CWM 800
Back Left & Right: CWM 650

All of the speakers are "in-walls" so they are intended to be mounted in an unported enclosure (your wall). Do you think a port in the rear would help clear up the bass and let the mid-range come through?

B&W tech support says that they are designed for an infinite case volume so the size of the enclosure should not matter. They also mentioned that a smaller enclosure will be tighter and more accurate while a larger volume will increase the bass but it will be less accurate. They also suggested filling (or at least partially) the enclosure to help dampen and negate the enclosures affect.

So far I have only tried filling my enclosure about 1/4 of the way with fiberglass. I'll try filling it more. It would be a pain, but I can install an internal baffle to cut their volume if the fiberglass does not help.