I was thinking of building my auto pc using a VIA mini itx and getting or building a case to fit into a DIN slot.

Now I'm wondering if under the passenger seat might be better. I also already have a micro atx motherboard (Soyo K7VME), memory, 3.5" hard drive and AMD Barton 2500+ to go with it that I could potentially then use instead if I built a short enough custom case to fit under the seat. I would have to come up with a low profile heat sink solution for the cpu if I were to go this route (perhaps make the whole top of the case out of metal to act as the heat sink?). I could under clock the cpu some as well if necessary.

Has anyone done this and have advice to give? Would a 200 W DC-DC power supply be sufficient? How would I hook up the 4 pin 12V ATX connector?

If I go this route, I also have a PCI TV and radio tuner card I could use. But to reduce the case height to 2 inches I would probably have to get a PCI riser (although one of the cards I have is pretty short already).

Finally I would probably be hooking up USB touch screen (or PS/2 touch pad), USB wireless (to sync my home music collection), USB GPS and maybe a USB FM tuner if I can't use the card I have.

I'm also tempted to try Windows Media Center as the OS especially if I do get a touch screen LCD since it seems well suited to a touch screen interface.