Zuck, don't worry about 4 ohms; the 8000(if you already have it)is a very heavy-duty receiver and should handle the M80s with ease. Note the lab results in this test.

Having said that, unless you have an extremely large listening room, I'd suggest that the M60s plus say a SVS 25-31 would give you even better bass than the M80s and still plenty of dynamic capability.

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Enjoy the music, not the equipment.