I mean if you were to just replace the video card, it wouldn't be such a big deal.
BUT, if you would like more bang for your buck and have no problem returning everything (Except for maybe the processor (3200), and the memory), then we can help you out a lot.
My build (in my sig) was less than 720$ for the actual system (but then shipping + tax)
Some would rank the rig in my sig better than the one you bought
Since you have 300 more $ than I had to spend, then you could get a really awesome build.