I have a Yamaha 765 and I'm stuck between Polk m60's or 70's. I hate to buy the 60's if I'm always going to wonder if I should have spent a bit more and got the 70's. But I'm not exactly sure if my unit is strong enough to power the larger 70's. I believe the Yammy puts out 665 watts and I dont plan on buying a amp anytime soon, if at all.