Ferguson, I have been driving the Epic 80/600 system with a HTR-5660 for over 2 years now with no issues. It does run warm/hot, but has never shut down. The key to your happiness is will be how loud you like to listen, and how big the room is.
At the last house, the system was in a 2300^3ft room (16x18), and the Yamaha was more than adequate. In this house, the system has to fill 10,000^3ft, and the Yammi just isn't cutting it. As the volume goes up, things fall apart rather quickly. The highs get very harsh and the mid bass gets sloppy. Luckily it has pre-outs, so adding an amp is very easy.
