Kord, welcome. You won't hear harshness through the M80s and associated receiver unless that's the way the program material is.

I'll add a suggestion that you seriously consider not limiting yourself to only front speakers. Surround sound creates a greater sense of realism, including 2-channel source materials which have the natural surround ambience contained in the front channels(there was no place else to put it)extracted by processing such as DPLII and sent to the surrounds where it belongs.

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Enjoy the music, not the equipment.