Another f**king stereo question, need a stereo EXPERT Options

[ninefourteener]

Last night I had Best Buy install some stereo equipment in my car. All of it was 100% new, and unopened, so it's highly unlikely anything was defective.

Already installed is a VERY nice Pioneer 8500 CD player

Installed a JVC 500 watt 4-channel amp. Not overly expensive, but not junk either.

Installed 4 brand new Pioneer 6.5 inch 3-way speakers in the factory holes.

In addition to my passenger door not opening from the inside, there are several other problems:

1) I can turn the volume about as loud as it was without an amp.... whether I use the volume on the amp or the stereo. Once I go above that, the stereo "shuts off" when bass hits, or.......

2) Occasionally, I'll get this rediculously loud "squelching" sound that won't go away until I turn the car off.

3) I spend $80 on a Rockford Fosgate insulated Amp wiring kit, but I still have alternator whine.

I have an appointment today to get their best technician (15 years experience) to "re-do" the entire thing... but I'd like to have a basic knowledge of what "could" be wrong. Basically, I'd like to know some good questions to ask, or solutions to recommend.

Please don't respond if you're just "guessing". If you're very familar with how this stuff works, I'd really appreciate any help you can provide. I'm not doing any work, but I don't want to just look stupid not knowing what to ask, and accepting whatever they tell me. Thanks.

Matt