I'm very late to the party, but thought I'd throw in my 10 cents. I have the S-150 system and a the Klipsch RB-75 system. They are both great for cinema. Above poster is correct that the M&K's are used in studio's. Usually the self powered versions. On the other hand Klipsch Professional line are often found in movie theaters.
The klipsch are extraordinary efficient speakers where and the MK's are not. You don't need a powerful amp to drive the Klipsch, but I suggest you have beefy one to drive the MK's. I personally find both systems are fantastic for movies. The klipsch definitely have a more in your face or big sound whereas the MK's are much more transparent. I agree with the above poster who mentioned the MK being a bit more difficult to get right in a room. It certainly takes some time to get it right whereas the klipsch are much more flexible.
Currently I have a Onkyo Pro 885 with D-Sonic IcePower amp pushing the MK's and it sounds amazing. The Klipsch are being powered by the Outlaw 990 and Adcom 7707 amp and also so amazing. When I powered the MK's with a B&K Reference Receiver, it didn't have nearly the sound or depth they have now. I think the B&K just didn't have enough power or that it just wasn't a good match.
I've had a few people listen to both systems without complaint. However one thing with the MK is that people tend to say it's easier to listen to at high volume because the sounds is so clean. The highs on the klipsch are a bit too ear piercing at higher volumes. This could be the combination of pre & amp etc. My girlfriend clearly prefers the MK system with blu-ray content over the klipsch. I will be getting a new pre/amp setup for the Klipsch system which will probably consist of another d-sonic and the new outlaw 997.
If I had to choose between one system, it would be the MK system, but I might miss the klipsch. It's just that dialogue with the MK is so real and natural sounding and when effects happen in scenes I find it easier to visually place them on the screen than with the Klipsch. However, the klipsch are brighter and excel a bit more when it comes to action scenes.
MK Setup.. The room has all new furniture, lighting, screen and projector.http://picasaweb.google.com/pgwalsh/...35143571395858