at one point I had 3 pairs of M80's (yes thats 6 M80's) for h/T with my denon 4802 with-out any problems at all ....
doubt this is of any help, but when I had call denon about main speakers setups, I do remember them saying that most of there avr products (non avr products like Home Theater In A Box non included)are capable of handling the 4ohm load but do keep in mind with the combination of the surrounds this changes your ohm levels (in most cases this puts the level more near 6ohms) also the resistance on cables will also have an impact.
