Muzz, from what you describe it does sound possible. The AVR would power the rest of the speakers, and the HK's amp section would power the m80's. I'm sure someone else will confirm this soon. In regards to balancing out everything, you would still do this with the AVR when you run the auto setup like Audyssey on the Denon's, or one of the others offered by Yamaha, Pioneer, etc..

M80s VP180 4xM22ow 4xM3ic EP600 2xEP350
AnthemAVM60 Outlaw7700 EmoA500 Epson5040UB FluanceRT85