I have very low sound coming out of my left rear surround (a 7.1 setup). When I go to turn that channel up it starts crackling, and it really doesn't get that loud on the test tone. When I switch the rear channel RCA's on the preamp (an Integra DHC-40.1) the problem then goes to the rear right.....SO I have thus determined it's not the speaker. It's got to be a problem with either the Integra or the NAD 2 channel amp I'm using for the rears. I'm having a brain fart right now, and need some pointers on how to narrow down the problem. PLEASE HELP!