I think you should go for it.

The Pioneer receivers are rated for 6 ohms nominal impedance. Most speakers rated 6 ohms nominal will dip to below 4 ohms at times. The lowest that the M80s go, in terms of impedence, is around 4 ohms. Because of that, they are even nicer on your amplification equipment than typical 6-ohm speakers.



In addition, I don't think that the Pioneer would be out of place driving 4 ohm loads. The reasoning behind this is that it is part of the THX requirements to be able to drive 4-ohm loads safely.