Run Xlobby frontend on one Front LCD sreen and have it play a DVD on a LCD in the Back of my car. I can install two video cards and have one run each LCD. The front would just be an interface for the ones in the back.
I have an nvidia card with dual out. I have ati cards on my other boxes. All my video cards have dual out. nvidia works best for htpc imho. download tv tool drivers for it and you get more options.