I believe Jason (Jakewash) has tried various combinations of centers. Two M22s in a horizontal tmmmmt layout worked well, but a single m22 either horizontal or vertical did not (or so I remember).
I'm a little out of my depth on this so maybe while you are waiting for someone more knowledgable to come along you could post a little more detail about how your center is physically set up (stand/cabinet type etc.)
I have done a lot of reading on this site over the last five months and do not recall anybody else having trouble with the timbre matching so I suspect it is a setup issue.
I'm glad you like your M60s. I had a chance to listern to them and the M80s at Axiom and they are both very fine speakers!!
