Bob, why are you so reluctant to run one M80 on your amp at a time as many have suggested?

It would seem this would be the easiest and fastest way to determine if it is in fact a single M80 that has a bad crossover component etc. If the amp shuts down driving either one M80 then you will know it is that speaker causing the problem, if it shuts down for both, as grunt mentioned, it is most likely your amp and the M80s do not like each other at which time I would then go ahead and purchase the QSC amp as I highly doubt you would have 2 speakers damaged in transit.

Jason
M80 v2
VP160 v3
QS8 v2
PB13 Ultra
Denon 3808
Samsung 85" Q70