Umm? Among the Axiom lines, the only 4-ohm speaker is the M80's. At any rate, I do not think the current 45TX will have any problems driving them at all. I also own the 45TX, and it has no promblems driving my 4-ohm Hales (along with 6-ohm VP150 and QS8) at pretty high volumes.
Btw, although I have never listened to the M80 in person, the owners here tend not to recommend the M80 unless you have a fairly large room with a generous listening distance. It seems that the M80 needs a plenty of room to "breath and sing."
