I'll get this started, hopefully others will jump in. I guess the first point is that Axiom's in-wall speakers seem to sound just as good as their regular speakers, which means the sound quality is extremely good. I have not heard W22s or W150s, but I have heard W2s a/b'ed against M2s and the only discernable difference was a tiny bit less bass extension in the W2s due to the smaller enclosure volume -- which is a non-issue if you have a sub. The QS8s are considered to be one of the best surround speakers available, period.
The sound quality will be excellent. Value-wise you do pay a premium for the in-wall design, but you do get a lot of advantages. I have not researched in-wall speakers as much as freestanding ones, but the price seems reasonable on the Axioms as long as you are comparing to other high quality speakers. You can get smaller, less accurate speakers (which would probably not satisfy in your room) for less, of course.
If you are looking for negatives, the main point to consider is that in your room size the 22s are big enough to handle both movies and music at normal volumes and sound great, but they are a bit small if you want to play very loud music in stereo. I stress stereo. As long as you use one of the receiver modes to expand the music signal out to all of the speakers rather than just the mains, I think the system will play as loudly as you want.
You will need to run the SVS with one port plugged (what they call "20 hz mode") to get the same kind of bass extension as the EP500, but early reviews seem to think the NSDs are quite good. I don't know how the two will compare for movies (the 500 comparisons I have seen were against a single woofer Ultra, not a dual woofer ISD/NSD), but for music the EP500 would probably be a bit tighter. That's a big room, so going with a big sub is definitely a real good idea.
That's all I know. Anyone else ?
