I have to go with MP3 because I've got a portable MP3 player that lives with me in my car because I can't stand most of the radio in the Bay Area anymore, and it's nice to have your own music when you go out of your local area instead of having to channel surf constantly.
Currently my Rio Volt has about 1200 songs on it. I think I can probably drive from San Francisco to LA and back without hearing the same song twice - well if their ranomization algorithm is good enough. :)
There is no emoticon for what I'm feeling now.