If you have a DECENT after market radio , you shouldn;t have that problem , if ou di , it'* 95% the wires connecting the radio and speakers, make you you have a solid grornd for the radio and the speakers have good contacts .
The factory radio should not have a problem with that at all , the lights in the radion don't have the same power source as the amp in the radio , that is why you can dim the factory radio and not aftermarkets.
If I'm wrong please correct me .

No I dont wear caps when I receive head.... Why would you ... dumb question... heh

by "a new amp" i was referring to having to buy a seperate amp to solve the problem.
my friends sister has a 99 sunfire and she bought a panasonic HU and it cost about $500 cdn. even with a professional install, the lcd display dims when the bass hits(she uses the stock speakers) this is what made my wonder about the HU dimming problem. do pontiacs have weak charging systems or something? my other friend has a 900W rockford amp (with two 10'*) in his b-3000 running off his battery and he doesnt have this problem...

PLEASE READ!!!!!!!!!!!
If you have a DECENT after market radio , you shouldn;t have that problem , if ou di , it'* 95% the wires connecting the radio and speakers, make you you have a solid grornd for the radio and the speakers have good contacts .
The factory radio should not have a problem with that at all , the lights in the radion don't have the same power source as the amp in the radio , that is why you can dim the factory radio and not aftermarkets.
If I'm wrong please correct me .

so rewiring with say 14 guage wire with good grounds should solve the problem?

The amp & radio have the same power input. Otheresise there wouldve been two red wires that come into the radio instead of one. Also how many of the aftermarket radios that you know of have a dimming feature on them. Majority of them have a contrast option that you can adjust so that acts like the dimming. Yes I know they come with the orange(w/ white stirpe) wire in the plug but that is a dummy wire. If your headunit dims with no aftermarket amps, it more than likely is the charging systems. Yes the Pontiac alternators do suck. If you have any aftermarket amp that you are going to install then I would run 12/14 gayge speaker wire to the speakers themselves. Normally from the front bumper to the rear bumper will be long enough to run the front speakers to the trunk.

Hmmm... :?

Is that because you dont agree with me or didnt look at it the same way as I do.

You must think on a different level , the amp in the readion and th radio itself have the same input, but the LIGHTING is attached to the rest or the car . that is why the lights turn on when the parking or head lights turn on . They also fade. The radion will still play if you clip the lighting wire. Think about it ,
Subject is dead.

Whats a readion/radion? Never heard of it. But wether or not the radio is going to play has nothing to do with the lighting system. You gotta explain better with what you said above. He wants to know why his lights are dimming with a stock radio & no aftermarket amp.