Seriously though, it sounds like you've done some research and have a good feel for some things.
1) HD Projectors, a lot of great choices out there, 3D will cost you more for a really good picture as far as brightness (keep in mind with the shutter glasses, you effectively cut the lumens in half since only one shutter is open at a time, so a higher costing 3D projector will have considerably better 3d imagery vs. a lower cost one, however, there are some $1500 3D projectors coming out right now.
2) There are a lot of discussions around here about watts and what they really mean. 110W will be more than enough to really tick off your neighbors (see my other post) and still sound great.
3) An 18x12x8 room is just over 1700 cubic feet. A 12" sub would be nice, but since the low bass sounds are what will annoy your neighbors the most (see comment #2 above and my other post), a 10" may work just fine. Dayton subs are mainly used in DIY setups and there are a lot of people using their Reference woofers for good DIY subs.
4) 5.1 is still pretty awesome. I am finally making the jump to 7.1 now, but there are so many movies that can't natively support it anyway, that 5.1 is still more than great. Also the jump from the M50 to M60 IS a lot more noticeable than from the M60 to M80, but don't tell that to all of the guys that upgraded from the M60 to M80. The M80 is pure greatness, but mainly in being able to get a little deeper in the bass area, and being able to be driven louder (ehem, neighbors???)
4b) I've had direct radiating (bookshelf), di-pole, bi-pole, and quad-pole (like the QS series) surround speakers, and especially for movies, the QS speakers are the best. I have QS8s and really, REALLY, like them. I have been running my 5.1 setup for 7 years with QS8s and like them so much that just last Friday, my order for a second pair of QS8s came in. I could have picked direct radiating like some smaller M2 or M22s, but the QS surrounds are awesome. If you are more into music, then yes, definitely look into bookshelf speakers. Mulitchannel music is more designed for precision mixes coming from very distinct locations, but for movies, you want a wider sound field the the QS speakers give.
I hope that this helps.
M60s, VP180, VP150, QS8s, M3s, SVS 20-39PCi, Shakers