Davey,

I use M22's in a 12' X 21' living room, and they push more than enough volume without distortion. If you really can't keep the M60's, I don't see any problem in you switching to the M22's.

And, if the extra savings can be put towards a better sub like an SVS or HSU, I'd doubly say go for the move to the M22's. I just switched from a budget Velodyne sub to an SVS PB1-ISD, and that was such a dramatic improvement (the SVS really is great) that I'd say go with the M22's and an SVS or HSU.

Good luck.