Chevy Suburbans are equipped with a Bose system. I recently yanked the Bose out of our Suburban and replaced it with JL Audio amps and Sub, Alpine head unit, and MB Quart Speakers -- HUGE improvement. I also added XM radio. Alpine Head Units come with something called a "MEDIA EXPANDER"
which is meant to be used with MP3's and XM Radio to fill out the missing pieces. I am not into MP3, but I can say that the MEDIA EXPANDER works really well with XM radio. Here's another thing -- instead of a CD changer -- here's what you do; The new Alpine Head Units will interface with an i-pod, taking over its functions and keeping it charged -- THATS THE WAY TO GO!! With a 40 Gig i-pod, you can store about 150 CD's UNCOMPRESSED. That's better than any CD Changer -- PLUS -- the i-pod is portable. Don't bother with a CD Changer, use an ipod -- it is like having a 150 CD Changer.