Don't worry about the ADA1500. I kind of doubt you'd turn it up beyond what an ADA1250 or even a ADA1000 could produce. It would be LOUD. Mojo, Do the ADA's protect against clipping in anyway?
Assuming that answer is no ... You'd probably pop the M60 on a ADA1250 before an ADA1500 because the 1250 (or 1000) would start clipping sooner ...