Leave the Pio on 8 ohms, the 6 ohm setting merely limits the current available. Don't worry about "matching" speakers to receivers or amplifiers, any amp/amp section designed in the last 20 years or so to have flat response (ie, not a tube amp) will sound the same.

Get the M80s and try them. Mine work fine on my H/K 525, which only puts out 75 WPC.

I am the Doctor, and THIS... is my SPOON!