I'm a big fan of aftermarket car stereo systems. A vehicle is far from a perfect soundstage, and older factory stereos leave much to improve upon.
However, you can go overboard with this stuff--especially in a performance street/strip ride. Though a trunk full of speakers, flip-down TV screens, etc. are sweet in the Escalade, they have no place in a GM ride that sees drag or road racing duty. It's a very fine line to walk.
That being said, I've found a great compromise: with assistance from Sony and Cartunes on Long Island, I just installed an F-body stereo, complete with an amplified 8-inch sub, that sounds outstanding and only added a few pounds more than a stock-type system.
Keep your eyes peeled for this web-exclusive feature on www.gmhightechperformance.com!