I bought the B&W DM603 fronts, CC6S2 center, and DS6 surround speakers about 8 years ago.
I used them with Adcom amps and processors, but recently upgraded to Outlaw 990/7125/LFM1+ combo.
The B&W speakers sound even better with the Outlaw products.
Even thought my B&Ws 8 years ago, I've had no need to upgrade.
I know B&W also makes high quality in-wall speakers that you would be loking for.
For the sub, I'd say get the Outlaw LFM1+. I love it.

Note that with any in-walls placement is probably the biggest performance factor (limiter) because the speakers are smashed against the wall (limiting performance), plus once they are placed you can't make adjustments. So in some ways it matters less what you choose (within boundaries of price/class reasonableness anyway) - the biggestest limiting factor in the whole system will be the fact that they are in-walls, and you can't get around that. That being said, the reasons I chimed in:
1) Note that the Magneplanar on-walls are a possible exception to the you-can't make adustments point.
2) You may want to consider the in/on-wall speakers from Axiom. They eliminate some of the smashed-to-the-wall point (while still providing decent internal volume - unlike most of the pure on-walls that are usually marketed to go with plasma TVs).
3) I'll put my second to Gonk's point that I would use an in-wall subwoofer as a last resort. Selection is limited, and the placement point may also be an issue. And because you usually have a lot of placement options with a subwoofer (and it sounds like you have some) the clean-look reasons for using in-walls is less in the case of a subwoofer.

One more point I guess - I did have have Polk in-walls and they did sound very good, in perfect circumstances (e.g. I had a Polk TC65i in-wall center channel blairing straight me through the audio-passing projector screen....that sounded great because placement was not much of an issue in that special case).

Definitive Technology makes good in walls also look at the Mythos

PSB, NHT.

Also look at Speakercraft. They actually make the in-walls for several other companies. You should be able to demo Speakercraft at an AV store. I heard a Speakercraft/SN 965 (on which the 990 is based) set up and was very impressed - never thought such good sound could come from in-walls...

If you have the wall cavity depth, the Triad InWall line sound nice, like the Def Tech's they're fully enclosed.

I would rethink the in-wall limitation if you value the sound. Also consider acoustic treatments...the best bang for the buck besides the speakers.

Remember the Magneplanars (1) don't involve any acoustic compromises since they're specifically designed for on-wall wall mounting, and (2) have no effect on the wall except a couple of screw holes, easy to repair with spackle if you ever want to move. No holes and no concerns about wall depth. The MMG-W (in pairs) and MMG-C center channel speaker (not appropriate for your needs since the manufacturer says it works best with a little space behind it) are available from Magnepan for 60-day trials with full return; you risk only the return postage. That trial (of the still-available MMG, a free-stander) convinced me of the superiority of Magneplanar sound enough that I've ended up with the larger MG-1.6QRs.

If you're going for an all in-wall system, then this is the only way to go for the subwoofer!
http://ibsubwoofers.proboards51.com/index.cgi

It's called an infinite baffle subwoofer and from what I've read, they rock. Of course, you need to be handy with power tools, or know someone who is.

Craig

THESE NHT's look awesome. Haven't heard em' yet, but I've always been a fan of NHT

I'd also second the psyprof1's recommendation of the Magnepan HT system. Especially since you stated 40% music listening. You'll probably want either that 7200 or 7700 amp to power them, but if you haven't heard Magnepans, you owe it to yourself to give them a listen. Properly driven, they leave box speakers in the dust. And you can take that to the O.K. corral.

Of course you'll still need the sub.

Craigo