I've got M80ti's in a room roughly 16' x 24' with a cathedral ceiling with very large skylight wells. I just got them 2 days ago, so I haven't gotten a lot of listening in yet, but so far I'm really happy. I have the Epic 80 system with an extra QS8 for 6.1, but I've yet to install the QS8's (difficult wiring problem that'll have to wait for the weekend). The M80's replaced a pair of Polk RT2000p's, the VP150 replaced a Polk CS300i. The difference is significant; I really disliked the sloppy bass of the RT2000p's, which I suspect is laregly due to the amp inside them (which can't be circumvented w/o tearing the cabinet apart). The M80's are a clear winner for tight bass here, and the EP350 does well on music (but not so well on movies if you like 20Hz response). The VP150 is much better than the Polk CS300i for movies in this room, especially for those not sitting dead center; the 2 tweeters made a big difference for me because no one is way off axis now.
The M60 shouldn't have trouble filling your room if fed enough power. If your room is like mine, the cathedral ceiling is beneficial. I get close to zero ceiling interaction between the mains and the listener because the ceiling slopes away from my mains. The front soundstage is precise. It's sort of a mixed bag behind the listener though. It's nice for movies, but takes some tweaking for multichannel music because there's a decent amount of midrange response coming from the sloped ceiling behind the listener. Here the ceiling is sloped toward the mains, hence echoing the mains to the back of the listeners head (first reflection). But it's quite a ways off axis, so it's not a huge problem. My system is dialed in for my current surrounds (Polk RT600i), but it'll be interesting to see how much work the QS8's will be to get right, since I'm fairly constrained on positioning them (all three have to go above doorways, with only the left one having doors).
