Even though it is easy to pull the original radio out, FYI, it is kind of a big deal to completely replace the factory radio. I'm not sure about the non-BOSE system, but I think all of the new generation sound systems are fed by a single ribbon cable that contains all the power, antenna, and speaker wiring. In short, you can't just pop a new head unit in without some major rewiring...plus as Dad mentioned pulling the factory unit kills some of the features of the car.
There is lots of history and creative solutions to this issue over on the audio board, so I would scout around over there. I think I also saw that somebody is now making some sort of converter that will solve the ribbon cable issue, but I may be wrong.
Y2K Midnight Blue SSEi
White Cathodes in Grille/ Blue Cathodes Under Seats