I have an Onkyo txds797 receiver that has 6.1 channel inputs and is cabable of 7.1 using an external power amp. currently i have a single surround back connected straight to the receiver, so i imaging i will disconnect that from receiver and connect two rear speakers to the external amp, and run a stereo audio cable from "surround back pre-out" on receiver to external amp. does that sound right? and another question... I am not looking to spend much money (or any if possible) so my question is if i would be able to simply use my older stereo receiver I have sitting unused in the basement? or does it have to be a "power amp".