I am looking at this amp to power Klipsch RF-82 II mains in a 5.1 setup. My main purpose is movies i.e. 90:10 ratio between movies and music. Any comments on this match, pls?? Also, do I really require to buy the pre-amp for NAD to be able to perform at its best or simply use the pre-outs of my avr (yamaha rx-v3900) and feed them into this amp??