Follow up to this. Luckily, someone else has an emepg at work, and we plugged his into my car and got the same result: power thump at start up and only playing through 2 speakers. It's gotta be the sled, but I won't know for sure until I pull the thing out. (it's a pain) As far as the thump, there is a power light on the amp, and it does not turn on until the empeg is turned on, so it's not that. Any other suggestions??