Eightbit.
I've got the same type of mockup that you are doing (waiting to borrow a digital cam to slap some pictures up here).
I'm using the Dreamcast though for a simple reason. Money. I had everything sitting around, I had gotten a really nice wheel and pedal set from Act Labs (when they were closing them out for like $15). I'm a driving game freak so I had about 15 driving titles laying around for it.
There are some really fun arcade ports that are great for having friends over. Daytona USA, 18 Wheeler, and especially San Francisco Rush 2049 are great fun, and you can get into them very quickly. Bleemcast allows Gran Turismo 2 on it and there are about 10 other driving titles I have that I'm working through (I got the cabinet just last weekend).
Its a great deal of fun, as I am sure you know.