SONY Power Amp question:

I guess that depends how loud you want to listen. They are 88dB @ 1watt, so that's 108dB at 100 watts. Since the Sony you say is 120 watts, I'm assuming that is into 8 ohms and the M5's are 6 ohms, for me, I would get more power. I think the biggest improvement would be to separate your 2 channel system from the surround system.

Yes it will run your loudspeakers but the SQ may be less than ideal (consumer grade HT receivers are not known for great SQ). 

thank you for your response .