Yet another somewhat crazy idea....
Since I still have the stock audio stuff in the Focus I thought up another possible alternative. I've done something similar when I had my Taurus and while it was a little rough around the edges, it worked quite well.
1 Mac Mini with ~80gig drive
1 power converter
1 6.5"-7" LCD touch screen(have yet to measure exact size)
* Stock speakers are ok for now, but eventually replace them with something better.
* There's enough room on the dash to eventually add a center channel speaker and enough room to spare in the trunk for a sub to come up with surround sound - this will likely require a surround sound capable sound card.
This would eliminate my stock head unit along with the FM tuner(which is fine, radio sucks anyway). Boot up time on the Mini shouldn't be too bad, my laptop does very well. Keyboard/mouse can be done via Bluetooth and adding music/video's could easily be done via the slot load optical drive or over a wireless link.