I didn't see it mentioned yet but you could use the same speaker for your center channel as you do your left and right...assuming the stud is not in the way.

Also are you against just getting M22's and wall mounting them? Alan has mentioned before you would get a nice increase in bass this was as well....

High Gloss Cherry
M60 VP150 QS8
Open for Auditions but please don't drool on the High Gloss