In reply to:

Can my receiver drive the M60's, provided I don't crank the volume?

M60s are very efficient. Power is logarithmic. IOW it takes 10x the power to make 2x the loudness.

That also means 1/10th the power reduces loudness only 1/2. That's why 0.1 watts on M60s sounds OK, and 1 watt is very loud.

A better receiver would be nice, but your current receiver can likely safely provide quite loud levels.