Re: MP3/Ipod vs. C.D.?
Almost everyone above is spot on with their conclusions about MP3 verses CD.
For all practical purposes, CDs, WMA Lossless, or 320Kbps MP3s (straight from the artist/iTunes) on SD/USB is going to be your best bet for car audio reproduction while being reasonably portable.
'65 VW Bus
(2) PG Ti 12's, (2) Aura Sound 8's, (2) SoundStream 6.5 coax, (2) Alpine Type-S 6x9's [rear fill], MBQ DSC1500.1D, RF 501X
'02 BMW 330xi (AWD coupe)
Harman/Kardon 12-speaker System Option - sounds good =)