Hi ddirado,
Putting the M22ti on its side will change the dispersion pattern of the tweeter and woofers. It will sound quite different but depending on the room and the placement, you may or may not find the change in tonal balance offensive.
The M22ti was not designed to be used in this orientation. If you search for "lobing" on the boards, there are several posts explaining what happens when you put the M22ti on its side.
You can always do an experiment with one M22ti on its side and the other in its intended vertical orientation. Use a mono music signal and switch from one to the other to see what tonal changes you hear.
Regards,
