Anthony, assuming a "need for a more powerful amp" if you get the M80s may lack any factual basis. Since the M80s have a slightly above average sensitivity(requiring less power than the M60s, for example)they and other 4 ohm rated speakers of similar sensitivity have been operated for years with modest receivers without difficulty. You appear to more concerned with the rated impedances of speakers than the power they actually require in typical home operation.

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Enjoy the music, not the equipment.