I'm just trying to figure out what you would do with that much computing power in a car. I know it's getting harder to find retail CPUs under 2GHz now, but why 64bit and a gig of RAM other than the cool factor? I'm not saying it would be bad (it would be a kick-ass system

after all), just a little overkill for something to play music, movies, and "war driving".
I've been looking at the
Mini-ITX boards, and now the Nano-ITX (same page)(only 12cmx12cm) Most of these boards have built-in audio, video, LAN, and MPEG decoding, and a lot are fanless. They're kind of like an Insight, small, quiet, and efficient

They don't offer much above the 1GHz mark, but you can also get away with a 50-70watt power supply, some of which can run right off 12v.
Looking at the fold-out designs for LCDs it looks like a fold-up mount would hit and block the air controls. Folding down would be too close to the shifter. I'm convinced I could live without the cup holders and just fill in that area like a few other people have done.
As far as the computer itself. I figured either behind the passenger under the rear deck, but then you can't really access it. Or get a nice looking case and mount it behind the passenger seat, maybe with an option to quickly remove it. And if you get a wireless NIC that supports an external antenna, you can mount the antenna on the roof for better reception.