Welcome Sean
If thin is not what you're looking for, I'd stay away from the M22s. The M3Tis are incredible speakers with a full, rich midrange and sparkling highs. It also has fuller bass which goes lower than the M22s.
However, if you can swing the M60s, I think you'll be astonished. As to that, I think the M3Tis will astonish you with their goodness as well.
Since you describe your fronts as "mains" I assume you are putting together a music and Home Theater system. The M60s are a really superb HT main speaker system choice.
For all that, the M22s are great speakers. If you read the reviews you will see that they are uniformly enthusiastically positive. The pair I auditioned just didn't do it for me, maybe it was a weak pair, maybe they didn't like the rest of my system, dunno. But, with a good subwoofer I'm sure the M22s are awesome in their own right, and the sub should fill in the lower octaves and elevate the M22 sound to the sublime.
