JohnK has given you probably the best advice you can get on your question. Here is an article from Audioholics briefly touching on this subject. One thing to note is your receiver does have main outs, if need be you could always add an external amp that will handled the M80s with out problem.

On the Yamaha website it does claim that the HTR-5660 can handle a 4 ohm load, although it does state the fact it has a 4 ohm switch. As you note in the Audioholics article it is not recommended to use it.


Rick


"A fear of weapons is a sign of retarded sexual and emotional maturity." Sigmund Freud