spindocttor

Now that I've finally got my TT coupe, I wanna put a stereo in it. I got the standard audio, as I couldn't see paying $1200 for the Bose. Anyway, I've got a few questions:

1. Do I need to keep the original head unit in it for the display/trip computer/alarm functions to work?
2. Can I put a CD changer in if I keep the original head unit? If so, what will it take to do it? How would it be controlled?
3. I don't want to add a lot of weight to the car as I'll be autocrossing it and taking it to the track, so I figure getting a removable bazooka tube is the best way to add bass. Is it?
4. If I put in a powered bazooka tube and a CD changer, will it sound ok?
5. What would the next step be - adding an amp (again, I want to keep the non-removable weight to a minimum), replacing the tweeters, or what?
6. Would using a portable MP3 player (got my eye on the 6 gig Nomad Jukebox) and a cassette adapter sound ok?
7. Any other suggestions?

Thanks.