FWIW - I'm going to embark on a poor-man's approach to something similar.

I ordered this in-line FM modulator from Crutchfield:
http://www.crutchfield.com/S-YRRTWlc5ocL/cgi-bin/ProdView.asp?g=227750&I=026EFM01

I ordered the Panavise car mount thingy. However, I have an older 20gb iPod that I keep in a Marware sport case. I ordered one of these to put on the panavise:
http://www.marware.com/cgi-bin/WebObject...Z9b2tM7dWRkCVbg

I plan on wiring in a std firewire car-charger similar to how "Mac" did it. I'll wrap the fw cable and the aux-cable together.

The total I spent is about $100 but I fully expect the results to be less spectacular (sound-wise).

As recently as 5 years ago I had a 6-disc CD changer connected to a factory car stereo via in-line FM modulator and I don't recall being put-off by the sound quality but I could be looking back through rose-colored glasses.

I'm not ready to replace the Rockford Fosgate setup *yet*. Maybe next year.