Being that GM is a car manufacturer I'm sure that a high quality sound system isn't very high on their list of importance to their cars.
After-market speakers might be able to handle a little more abuse than the factory speakers but in the end you'd probably wind up blowing the new speakers too. The best thing you can do to help protect the speakers would be to ease up on the volume control and/or back off the bass settings on the EQ a little.

