Just put all my music onto a USB stick, I'm using that now instead of an Ipod. Very handy, I put all the files on as a mixture of formats from my ITunes library, the car system sorts it out and gives a reasonably good interface menu. Even sorts out the folders that I had the files in.
I think that this is actually sounding better than doing it through the Ipod. Better dynamic response, although the music source files are the same. Maybe it's my old ears, or maybe the Ipod method introduces a small reduction in quality.