Are you SURE you don't have Monsoon? I know for SURE you don't have Bose because in 02 they switched from Bose to Monsoon to be the top of the line.
How many speakers do you have? 4, 6, or 8? If you have 8 you will probably have the Monsoon system. The easiest way to check though is look in your trunk. Pull that plastic piece that is held onto the back wall by magnets down, and look on the driver side of the wall. If there is an amp there that says Monsoon, well its self explanatory.
My car came equipped with the Monsoon system, but the previous owner put in a new H/U and didn't like it I guess, so they re-wired the car.
This is what I'm getting for my car...link may or may not work though.
2004 Chevy Silverado Z71 - 15% tint, FTDRL, All-on-high, 5000k lows/fogs, tinted tails, color matched grille, Sound by Kenwood.