I have found that B&W makes some of the best sounding in-walls around. I have used many different models, and have loved them all. The CWM 650 is a great speaker.
BTW, I have also found that 8" 2-way in-walls have a tendency to sound quite boomy, and I generally shy away from them in favour of the 6.5" 2-way.
As for the importance of the various speakers, I have to disagree with Rob in his feelings that the "rears are not nearly as important". With todays digital surround, your surround channel speakers can get quite a workout, and they have a large impact on the overall sound of your system. I would suggest using the CDS6 in-wall di-poles for your surround channel. They not only look very nice when installed, they sound excellent. The di-pole array really helps create a dynamic, diffuse surround field.
Add a good subwoofer (DON'T BOTHER WITH IN-WALL SUBS)and you will get great sound!!
