How big is the room you will be listening in ? That might help with the "M60 8 ohm vs. M80 4 ohm but might need separate amps" question.

M60ti, VP180, QS8, M2ti, EP500, PC-Plus 20-39
M5HP, M40ti, Sierra-1
LFR1100 active, ADA1500-4 and -8