I am not sure why you are still getting the distortion. I have not had any real distorting of my woofers where they sound mechanically overdriven like a crackle. It could be that the woofers were damaged from diving the XPA-2 into clipping. The XPA-2 could have an issue. I am not sure the protection circuit would cause that. Maybe the Denon preamp is being driven too hard, but I doubt it. I didn't have any issue cranking my Onkyo or yamaha with the XPA-2. If it is a certain frequency it could be something is slightly loose that resonates at that frequency. I think I would consider talking to Lonnie or Nick at Emotiva about the issue. Or check your M80s with the Denon and see if they distort.

This is a tough one to guess at.

M80,VP150,QS8,ERD-1,XPA-2,XPA-5,UMC-10,PS3,XBOX360,Dish VIP622,PB13 Ultra,Panasonic PT-AE3000U