there are many many threads on this site with similar budgets, i suggest you look at those, and come up with something from there. the most popular build in this budget range (and for good reason) is an i5-2500k + p67 mobo + dual 6950s. The 6970 is a better card, but the performance increase does not match the greater increase in price. Dual 6950s are very powerful. A good 750w psu will be enough to run this setup. If you want what are perhaps the most recommended components:
IMO, with your budget you could probably squeeze one in if you want. Depending on the size you could probably put some games on it, but you could buy a small capacity one for your OS only, if you want.