Celtic Heroes

While I'm an Apple fanboy I occasionally want to play some newer games on my computer, and unless I'm rocking a 1500+ Mac that is not going to happen. I really do like the look of the Mac Mini and I love the ability to VESA mount it to the rear of my monitor(I'm OCD about perceived clutter), but from what I read and Intel HD 4000 graphic system is horrid for gaming. So, I'm thinking of building a Hackintosh to dual boot XP just to play the occasional game. What I am wondering is what is the smallest system I can build with a dedicated graphics apple, and would said system be able to mount to the rear of my monitor?