stereo chevy impala

I have a 2008 Chevy Impala LT, it has NO Bose or premium sound system, There is NO factory amp as well, I believe it was a fleet vehicle (Very Basic) What my problem is that I'm trying to install a Power acoustic Stereo (after market) I previously had the same set up and wire harness installed...

hey everyone, i was just wondering.... I have a 2000 Chevy Impala, which for some reason has an amplifier in the trunk,.? anyway we took out the dash and stereo and were going to wire an aux cable to the stereo, just messing around. We cut a purple wire and suddenly my speakers got louder...