Well you can always put a kenwood deck in the new car, making sure it is compatible with the music keg. Failing that there is the Omnifi, which has an opensource "firmware" available. It is a harddrive based player (easily able to upgrade the drive size) with a DIN size controller. No voice indication, though. It plays wma and mp3 only, though flac has been in the works for a while. You need an aux in capability for the car deck (sometimes available thru a CD changer port, or other). We had the Omnifi in our subaru feeding into a Nak deck - didn't like it nearly as much as the Phatbox/music keg. Then there is the Rio Car/Empeg - it's a deck that mounts in a DIN slot and has up to two hard-drives in it. No built in amp, but there was an add-in tuner available. The two devices have not been produced for years (the Empeg was a very short production run) and are available only via e-bay or user forums, etc. And of course there is always the Ipod, or other MP3 player - most new cars will have an aux in in the front or some kind of Ipod integration; again in my opinion that falls far short of having a phatbox with 320gb drive and giant gapless FLAC collection.
Cheers.
Jeff