I like HDMI for monitors because of ease of wiring and ease of configuration, but you usually only find one HDMI port. Get as bright a monitor as you can find. I really like ELO touchscreens, having been using them daily at work for many years. They are expensive though and not really any brighter than any other monitors. You need brightness in a car because sunlight washes out the screen easily. I just have a Chinatobby 8" HDMI screen for now, and it's not very bright, but is acceptable. It's not capacitive, but the single point touch works fine.
I built a Voom2 housed I7 Mobile based unit, and it seems to work great even though it is running at 2.1GHz. It turbo's at 3.1GHz when needed, but only uses 35 watts.