Can you please describe how far from the front and side walls your M60s will be placed, how far apart they will be placed and how far away you will be sitting? Is it rock you mostly listen to?

Your best bet for softening the tweeter is your tone control. Axiom at one time made in-line resistors available for the tweeters. You may or may not like that "fix" if it is still available.

House of the Rising Sone
Out in the mid or far field
Dedicated mid-woofers are over-rated