Just out of curiosity, why do you absolutely need a dual core machine? I don't know what your exact plans are, but for a pinball machine that has 2 video outputs, I simply do not see the need for even a 2 Ghz single core machine. What are you planning on displaying on the screens? If it is just video, then a single core would do, and if it is 3d stuff, the vid card would do most of that work.
As a point of reference: My last laptop was a single core 2Ghz machine that I had 2 screens attached. I would often have one screen showing a movie as I played a game on the other screen (usually Dungeon Siege). This all with a bunch of programs running in the background and often a torrent DL or two in progress. I never hit 100% cpu doing this. And bear in mind, this was a laptop AMD processor too.