Lots of 5-7 inch LCD screens out there...
Add 1 mini ITX PC board, case, processor, memory and hard drive.
Wireless network card (to manage files while its parked in your driveway).
1 digital audio output card.
1 FM tuner card.
1 GPS Nav card.
You'd have access to any music file you can come up with.
Drawback is no just throwing in a CD.