I currently run a 55 watt Sonic Frontiers tube amp with my M60ti's, at 8 ohms. Provided I rewire the amp to 4 ohms, should I feel confident this will be enough power to drive the M80v2's?

Should be just fine. 55 watts is pretty high for a tube amp, as far as I know. Generally, I think the formula is 3 tube watts is equivalent to 1 solid state watts.

MM, welcome. Regardless of what type of amp that you're using, it's probable that 55 watts wouldn't exceed the maximum that the M80s would use on a brief peak, except in a very large room playing material with a wide dynamic range and using a very loud average level. So, unless these latter factors apply in your case, yes you can "feel confident" that you don't need a higher maximum power capacity. Since the M80s are slightly more sensitive than the M60s and therefore use less power for a given loudness level, if you're okay with your use of the M60s now you should have no problem with the M80s.

Thanks for the reply. It makes sense and was very reassuring.
It is about the music. I really enjoy the Power One and the pre, which is an Audio Experience Symphonies Plus.(redone with Cardas GR capacitors)

Cheers!