I don't know why you would want to play games on the carpc, as your car battery would certainly be dead in less than an hour if you run a powerful CPU/graphics card combo. This of course is assuming your engine is turned off, as it would be crazy idea to play games and drive simultaneously.
If such a high end graphics card is necessary, go buy a desktop-replacement gaming notebook and mount it in your trunk. It could double as a computer that you can grab from your trunk later for LAN parties. Install a notebook lock in your trunk too.
