I agree with canadian guy that you would need a sub and a center channel.
I think, though, that if you watch a lot of movies, you would want QS 4's in the back. If you listen to a lot of music, M3's will sound much better. It's also just a matter of taste. I never really watch high action movies, so I dislike the sounds of QS's in the back, since I mostly listen to music, and sometimes watch movies.
Could you tell us what equipment you will be matching this with, and how large your listening area is? This will greatly help us help you address your situation.
