Well the QSC amp, has little or no reason to blow up. It is brand new has way more protection then a 1980 amp. It was built to handle 4 ohm loads. If it shuts down at all...then the speakers are the problem. That amp will put out 700watts at 4 ohms..way more then i would ever need, or anybody could be in the room to hear. The chance of this amp getting toasted...is pretty much nil.....has WAY better protection circuits then the old amp.

Like i said..this is NOT rocket science. It either works or it dosen't.

NOT that I don't think your tests are valid.....just not willing to risk the 504 amp. The M80's are NOT going to damage the QSC...if that amp shuts down...the speakers are at fault..period.