Depending on what level you're looking to go to I think the 800 series could be overkill. Here's why. Your CDM1s are probably fine for home theater use, and in my humble opinion the center channel and sub are the most important speakers to get right in terms of impact/enjoyment factor.
I'm not a fan of B&W speakers overall although I respect them a good deal. But I have to say a friend of mine had a Matrix setup and had the Matrix HTM center channel speaker (the one with one midwoof and the tweeter mounted on top -- see link below), and that speaker just sounded dead on balls perfect for TV and movies. No chesty colorations, plenty of grunt for deep male vocals, no discontinuities in sound from left to right so prevalent in many centers with two midwoofs flanking the tweeter, etc. If I were you I'd keep my CDMs, find a used Matrix HTM and possibly upgrade the sub (not sure how good your is, but maybe look at something like a Hsu STF2) and just enjoy. I'd bet there's enough house sound synergy between the Matrix HTM and your CDMs to be more than compatible.
Here's a link to some images in case it's helpful:
http://www.google.com/search?q=b%26w+matrix+htm&hl=en&prmd=imvns&tbm=isch&tbo=u&source=univ&sa=X&ei=mUewT-3qLYGX6QGk87SjCQ&ved=0CH8QsAQ&biw=1024&bih=591
Anyway, for what it's worth and best of luck.
I'm not a fan of B&W speakers overall although I respect them a good deal. But I have to say a friend of mine had a Matrix setup and had the Matrix HTM center channel speaker (the one with one midwoof and the tweeter mounted on top -- see link below), and that speaker just sounded dead on balls perfect for TV and movies. No chesty colorations, plenty of grunt for deep male vocals, no discontinuities in sound from left to right so prevalent in many centers with two midwoofs flanking the tweeter, etc. If I were you I'd keep my CDMs, find a used Matrix HTM and possibly upgrade the sub (not sure how good your is, but maybe look at something like a Hsu STF2) and just enjoy. I'd bet there's enough house sound synergy between the Matrix HTM and your CDMs to be more than compatible.
Here's a link to some images in case it's helpful:
http://www.google.com/search?q=b%26w+matrix+htm&hl=en&prmd=imvns&tbm=isch&tbo=u&source=univ&sa=X&ei=mUewT-3qLYGX6QGk87SjCQ&ved=0CH8QsAQ&biw=1024&bih=591
Anyway, for what it's worth and best of luck.