I used an double din lcd screen with a mac mini in my last car.. worked great, had wifi, bluetooth, ect.. all hooked up to my factory stereo wiring..
Like tusk said, there really isn't a car stereo out there that will have input for a computer of function like one. I used the Lilliput touch screen on mine it was like $350.. it has hdmi & VGA along with RCA, ect.. it's simple. YOu really only need a computer, powersupply to run it, and a monitor.
I'll be installing one again in the ITR over the winter. It's a pretty simple process once you have everthing.