You're not going to get satisfaction from talking to Emotiva about this issue. They - predictably - assert that the M80 is difficult to drive. However, the Emotiva amps seem to be the only ones that have that difficulty. It's not a "pairing" problem between the Denon and the Emotiva. It's not the M80's causing the distortion. That Emotiva amp has a problem with difficult loads. Follow Wid's advice and get a Rotel or one of the brands Ken mentioned. Do a forum search here for Emotiva and read the many, long, detailed threads that detail the agony of people like you that have tried this before.

A pair of Outlaw monoblocks might fit the bill.

Look, I desperately want to like Emotiva products. Their company is run by fine people. I like their style. I like the value proposition. But there is something about the engineering inside the XPA series amps that just doesn't play nice with the impedance presented by certain speakers.

As others have mentioned, if you're not hearing the distortion at similar volumes by simply using the Denon's onboard amps, that should tell you everything you need to know.

bibere usque ad hilaritatem