This one is a hit or a miss imo. I have the Alpine DVA-5210 and its spec shows that it is mp3 compatible... However, when mp3's are burned to a DVD, it refuses to read the data, a CD-R is fine. Check when buying a head unit that it states it is DVD-mp3 compatible as just mp3 compatible normally means 'only on CD-R'! Still the 5210 is a serious peice of kit and sounds fantastic.
Only a few CD-players can play MP3s from DVD-discs. JVC has a few players, they promote the feature with a "Giga-MP3"-logo. I'd recommend the KD-AVX1 player which is quite cheap now with the new AVX2 player on the market. JVC still retails the AVX1 though. The AVX1 has a 3 inch color display, the AVX2 a 3,5 inch widescreen color display. Both can play mostly anything thrown at it; DVD-movies, VCDs, CDs, MP3, WMA, all kinds of burned CDs and DVDs and so forth. The AVX2 also plays DivX-encoded movies(!!). Yeah, and they also have an RDS radio
JVCs are compatible with the steering wheel remote control buttons in our Vauxhalls / Opels. JVC supplies an adapter for connecting the player to the car.