Light,
Maggies are generally not a bad load for a good amp like Pass. IF the new 3.7s follow Magnepan pattern, there should be NO impedance dips to weird lows OR any huge phase angle stuff to deal with.
OTOH, they ARE fairly low sensitivity which is made up for by being dipole. Damping factor? Anything over maybe 20 will be fine. Even low damping tube amps work well, if enough power. The air damps the mylar pretty well, and being a single sided driver, not as coupled to the magnets as a good cone driver. The push/pull 20.1 may be slightly different.
You are right about dynamics and power, though...
Power users of panels like some of the big 'd' offerings. Spectron? massive.
Also, if Pass amps thru the line are anything like the XA 30.5, while it is 30x2 into 8, pure class 'a', the redline is almost 200x2into 4 in a/b. If the XA 60 does the same thing, it should be quite sufficient. Whoever said to look at the meter had it right. If the bias stays in 'a', or just a flicker periodically or on crescendos, than that is probably enough juice.
Given my listening habits (important for all to consider) I'd probably be quite happy with the XA30.5 level amp. The 60? WOW! OR if I had really deep pockets, a pair of 30s, as biamp!
Are the 3.7s fused? My 1.6s have a 4amp mid/tweet. I doubt the whole panel draws 8 amps at the limit. Thats just over 250 watts RMS..... How would that work out for dynamic power? Lots, I suspect.