I used to have a Sony 10 CD stacker in my Range Rover which was used on a number of trips. It never once skipped even after spending weeks on corrugations and putting in air time on a couple of occasions.... I can't reccomend it enough.
In my Camel, I now run an 40Gb iPod into a Sony head unit via a Dension iPod cradle. The cradle lets me mount the iPod on the dash, re-charge the iPod and control it via the Sony controls. The sound quality is great but the controls are a bit fiddly until you get used to it.
A little note about MP3 players... Make sure you know how the innerds work! A HDD based unit might not be much use in an off-roader if the HDD is constantly spinning. The bouncing around will damage the HDD which in turn means that the MP3 player will go kaput! Make sure it's either a solid state unit (e.g. Memory stick based) or one that caches large chunks of audio to RAM before playback (such as the iPod).
HTH
Mark.
