Just got my MKII 20GB Amber installed a couple of days ago in my 1998 GMC Jimmy. I got the stereo and an MTX 4-channel amp installed at Circuit City. It played fine (just the ride back home) when they first installed it, but now I only get sound out of the right rear and left front speakers. Also, there is a thump on startup of the empeg. I don't think this is the negative spike bug because the player doesn't lose its song position and it doesn't thump when I turn off the ignition. It's only when I turn it on. I took it back to Circuit City and they said it was the empeg. They checked the RCA's and the amp with testers and say everything is working fine. Well, I went home and plugged my empeg into my stereo output through the RCA's. My stereo has 4 speakers and it plays out of every one of them, so I'm pretty sure it's not the empeg. Anyone know what this could be?? The amp meets the specs and I'm running monster cable throughout. Could it be just bad grounding? I trust the "pros" at Circuit City know how to ground it correctly.....