No, the only full-color GPS/DVD units I've seen don't have hard disks. They're MP3 CD-R only. You're looking at an empeg-plus-GPS/DVD, or an in-car computer.

Even if the MP3-CDR players could play a recordable DVD full of MP3s (I don't know if they do or not), you're only looking at having a small subset of your collection on a given disk (4.7 gigs), so you're still back to swapping CDs, the very thing that the empeg was supposed to fix for you.