I voted 'Its more complicated'.
Nice looking setup!
I have the same receiver, and a set of M3's going across the front.
With regards to music, I'd try to find a good recording of whatever genre/artist you enjoy and listen to that first. While the M3's are reportedly the most forgiving speakers in the line up, I find that bad recordings sound BAD.
I would also look at isolating your speakers from the shelves they sit on. The M3's do resonate some when listening at elevated levels and send vibrations through whatever they are sitting on.
I can't comment on the role of the center channel speaker as I opted to get another M3 to serve as the center. No difference in tone or timbre to me.
BTW, you know that a bigger sub is in the cards for you down the road right? Its just a part of the upgradeitis that eventually gets everyone. Except for fredk maybe.
