M80 will definitely have better bass output. I think you better to keep your exelent M60 who actually are 8ohm speaker vs 4ohm from the M80. Yes your actual gear could drive both pretty well but M80 require a little bit more power to give you best result. So like i said, before spending extra buck to upgrade from the M60 to M80, get some new amplification. wink
GL

Nad C356 DAC & C515
Axiom M3v3
Grant Fidelity RPF-120 MKII
Analysis Plus Black Oval 12&10
JRiver 19