When I had the chance to A/B compare M2 with M3 (in an admittedly unprofessional way) I found the difference in midrange to be much less than I was expecting. There is a clear and consistent difference -- it was literally as if the vocalist was standing a couple of feet further away with the M3s -- but the soundscape and imaging were indistinguishable between the M2 and M3. I mention this because the latest M2s are full members of the "M2 / M22 / M60 / M80" club in terms of sound characteristics, at least since they picked up the standard 1" tweeter a couple of years ago.
I imagine the soundscape and imaging would be just as good on M40/50 as with the M22s... but I expect you would have to go to at least M50 to get a noticeably "bigger" sound. It's hard to say for sure because that "bigger" sound is so darned hard to characterize and translate into speaker characteristics. The problem is that once you have stretched to M50s the 60s aren't that much further away
I'm wondering if it would be worth experimenting some more with placement, maybe you're sitting too far off axis to get the best sound from the 22s or something like that ? Any chance you could post a pic of your layout ?
One of my concerns is that from your description of the room setup you might have trouble getting 60s into the right position... you need to figure on the front of the cabinets being almost 3 feet from the wall in many rooms. On the other hand if you could use the entire 12' width of the room and have your seating position near the back wall, the M60s would be able to really shine.
