First of all, what an amazing set up!! Something I've always wanted to try, but never had the time or money... However, when I was thinking about it, I was considering using a mini mac with a fold out screen. Its small enough to mount in the dash like a head unit, as its the size of one, and the fold out screen would mount on top giving it a very clean look with no gaps. Also the mini mac is very good with multimedia and plug ins...