I have a reciever (yamaha htr5760), it has multi-channel inputs and pre-outs for each channel (fx2,sx2,sbx2,cx1). Do I need a specific amp for ht with 7 channels? What are these preamps and amps and could I still use my yamaha's functions to set the levels and programs for movies, like I want a power amp or something to make the power stronger. How does this work? Am I better off returning it for a htr5790 or rxv1500 before the warranty expires? Thanks