The HK has two sets of speaker outputs - the second button from the left is labeled Speaker 1 / Speaker 2 - I'll assume this turns on each pair of speakers. The back panel has two sets of speaker outputs labeled as 8 ohms - the amplifier specifications are 100 Watts per channel driven into 4 ohms and 80 watts into 8 ohms. The owner's manual is not available on-line to see if there is a warning about driving two sets of four ohm speakers. The M80's are 4 ohms, the M60's are 8 ohm speakers. This amplifier will not likely damage your speakers but I've found that distortion (clipping) rather than power kills more speakers.
