When does theft loc go off?

I want to get an aftermarket deck for my car, but I heard that if I switch, I lose a lot of bass from the OEM Monsoon deck. Well my friend has a Sony deck laying around that she said I could hook up to see how bad it would be. Only thing is I don't want to go through the whole process if my stupid theftloc is going to kick in when I unplug the harness. Is there a way to turn that off? I bought the car used so I would not know the code. Thanks! Oh it is a 98 Camaro with Monsoon.

As soon as the radio loses power, the theft lock will take over.