Have you seen or heard anything about mp3-player "MP3 Stock" for use in cars? As far as I understand, this is a home-built system.
http://ayb.hypermart.net/videos/ (http://ayb.hypermart.net/videos/)
Please notice the lcd-screen coming out when starting the car engine, the crossfading function and the voice confirmations.
Edit: Just watch out for pop-up windows