Rook, welcome. That Yamaha should be fine with the Epic 80-600 in the vast majority of setups. As is true of all amplifiers, including those in receivers, if they get driven hard enough and long enough their protective circuits will shut them down, but generally there's no problem when they're used sensibly. Note that the "massive speaker system", as you called it doesn't necessarily require massive power; in fact very often the bigger speakers in a line are more sensitive than the smaller ones and require less power. This is the case with the M80s, which require less power than many smaller speakers.
