Use irmp3 (
http://sourceforge.net/projects/irmp3). I found it the other day and it's EXACTLY what I was looking for. Works a treat so far - sounds like I am doing a similar thing to you. Let me know how you get on!
I've got Mandrakelinux but no carputer yet (I'm waiting for the price to come down on the most expensive parts). It's fairly slow to boot at the moment but I think it could be optimised.
Have you made your own case for the 20x4 LCD screen? If so, how did you do it? I think that's the next job for me...
Is the onboard sound on the EPIA 5000 no good then? I think that's what I was going to get.
cheers
ning