I have a Sony STR-DG500 receiver powering my 4 in ceiling speakers. Lately I have been having issues with the rear two speakers popping on and off. Today the two rear speakers are not working at all. I swapped input wires on my wall plate from front to rear and now the rear speakers work but the front do not. Not real savvy with audio equipment so before I go buy a new receiver, is there anything I should check/troubleshoot first? Thanks in advance. Worth noting, I have been having problems with the left rear speaker for quite some time where it would not produce sound, running an auto calibration usually rectified it, until it no longer did. I replaced the two rear speakers and all was well up until about three months ago when the above mentioned issue started. I am trying to figure out how to post pictures of the back of the receiver and the wall plate.