Generally speaking, denons handle the m80's pretty well... However I personally have not tried any of the "lower end" denon models with the m80's so I am not sure.
I think the worst thing that would happen is one of two things:
a.) during loud portions of music or movies you could hear some audible distortion.
b.) it is possible that at louder volume levels the receiver could shut down. I believe that only if you kept repeating this over and over again could you possibly see damage to the receiver.
I do not think you would damage the speakers.
I (and many others) have driven the m80's with my 130 wpc denon 3808 with ease. Maybe someone who has tried a model simlar to yours can chime in?
