Regarding the "its too much trouble to transfer files between a car PC and a homepc" issue. Assuming you have WiFi and basic knowledge of the windows home networking environment....
Setup a command line batch file to transfer and sync the files with nothing but A double click. Or better yet I'm sure there's even a solution or two out there that would automatically sync files whenever your car is in range of your network.
doesn't get any easier than that!
I've just been convinced that my next spare mother board isn't going to be another htpc... lol