1. You linked to an AOpen, not an ASUS
2. The eBay carputer uses a VIA C3 processor... POS... (literally they're used in point-of-sales machines, but they are simple and suck for anything requiring grunt).
Have a look around the forums at http://www.mp3car.com/ for a range of solutions - in all honest I think the easiest solution is:
- Cheap LCD screen (fold-out, touch screen etc) from eBay
- Laptop (whatever generation, if you already have one like I did then it's great, mount it under the passenger seat and just take it out when you want to use it as a laptop). Laptops are great as A: They don't drop power when you start the car, or turn it off for a few minutes etc B: Make troubleshooting easier when your in-dash screen doesn't display anything and C: have a built-in keyboard etc
- 12V inverter-> whatever laptop requires... these are $50 from supercheapauto, could probably find them even cheaper on eBay etc
Once you've got that, it's time to go nuts with software