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It would be a crying shame to blow a new Onkyo because it couldn't push the M80's. If I'm playing at moderate levels anyway, would the M60 serve me well? I've heard it has comparible mids to the M80's and possibly a more accurate treble.



You won't "blow" the Onkyo. It will self-limit and return to normal operation after it cools down.

The M80s are almost twice as efficient as the M60s. This means that you need almost half the power to achieve the same sound pressure level. I can't comment on how the 60s sound compared to the 80s but maybe Randy can.