60hz is just fine, you could even try 50 if the reeiver will let you hit that odd number. I would also try 40 just to see how it sounds, then go with which ever setting you prefer.

The Yamaha(looks like the 861 is the comparative) should handle the M80s, at worst it would go into protect mode and then you would know that you need to add an amp to run them.

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