I would go with the VIA cpu at 1 ghz, its what my friend used in his subaru. With you current set up I'd be worried about how much power you are pulling. When you get the VIA you are down into min atx size, and that means you could put the computer under your passenger seat. Then I would get a slot feeding dvd, so you do not have to worry about the slide out tray getting bashed off. Then you have your touch screen be your display, and you are all good. and if you need more hard drives, just get external ones you can mount else where.

1995 ford contour v6 5 speed , even though its not mine yet... http://www.cardomain.com/id/hyperlitenerd