Audio Systems: volume drops out when i slam the door and when i go over bumps, rear cargo area, amplifier section

Question
I have a 1997 chevy suburban 2500. I just had an Alpine Model: CDA-9885 deck installed after I thought my factory deck was going out. But much to my surprise the problem still exists. I went to B*** B** and had my deck installed for $5 since I had purchased it there. The tech installed it and tested it. Everything was sounding great. He pulled the burb out and I climbed in and hooked up my iPod and cranked it up and NO SOUND! We sat there and troubleshot it for 45 min. and agreed it had to be something with the amp for the rear speakers or a loose ground wire or both. he said he didnt have time to deal with it and had to go on break so i got pissed and left with about $400 worth of no sound and accessories. I CANT locate the amp anywhere.  I've torn the entire back end apart b/c the tech ran the make/model and said it was located in the rear cargo area. Guess what.... nope, not there. Then an online forum said it was under the dash to the right of the break pedal assembly and as far as I can tell it's not there either. I've checked in all of the other obvious places too... under the driver/passenger seat, the entire back end, under both sides of the dash, and even in the center console even in the glove box.

1. Where is the amp located?
2. Is the amp my problem?
3. Where is the ground wire grounded out for the stereo?
4. Should I just buy an aftermarket amp and have it installed?

Any help or guidance in the right direction would be greatly appriciated. Thanx

4. Where is the ground wire grounded out for the stereo?

Answer
hi the amplifier
is under your seat   but it powers only the rear 4 speakers not the drivers door
If you have the bose system the amplifier are inside the front doors with the speakers

if the problem is not the amplifier it is inside one of the doors ,one of the speakers is getting short going to ground this makes the radio to shut of the amplifier section before it burns

open all the  door play the radio half way volume  and walk around the truck hit all the door speaker location with your hands hard until you find the wrong speaker

do this before you look for the factory amplifier

there are 2 more speaker in the back roof
good luck hope it helps you find the problem