Hi mazzum,

I can't comment on the M3's (although I'm sure they will work nicely), I just want to make sure you are aware that with 5.1, there is no such thing as "rear surrounds". Surrounds in a 5.1 system should be on either side (maybe slightly behind) of the listener facing toward each other. They should be a few feet above your ears.

Here's a link to Dolby's speaker setup guide. http://www.dolby.com/consumer/home_entertainment/speaker-setup-guide/index.html

Dave
Audyssey Setup Guide