Aramazd
Deity
All right, I wasn't sure about it.A lot of mobos are micro atx, but it leads to a very crowded case. better to just spend the money for a full size case. If nothing else, it allows room for a better cooling fan on the cpu and is easier to work with.
So Gary, I would suggest Zelig's build, but if you want a GPU for gaming you could get a 8800GTS if you don't mind going a bit over budget.