I use a 80 gig iPod strictly for my car (using the direct line out via the iPods dock outputs).
I chose it for its capacity and many accessories (should I ever decide to buy any)
Its MP3 so I dont expect sonic grandeur , and now that its totally full (18,000 songs) I rarely listen to the radio in the car.
These days I rip @ 320 bit or higher, w/ the 10Hz cutoff feature disabled. I only rip my cd's I never download from the iTunes store, crappy bit rate. for what they offer I can do better buying used from the local used store or amazon.
I also dock it to my back yard stereo, w/ a Tune View dock, for boat drink simplicity.
Tune View iPod DockThe only thing I really dont like is the cryptic way the music is stored on the ipod. You cant navigate thru the iPod as if it were a flash drive, its just a bunch of gobbly gook.
unlike a zen which I have for my son.