I'm building a new computer, but my budget is limited. At the moment I have the (AMD) HD 5830 1GB listed as my card, but, ideally, I'd like something a little bit cheaper but with similar performance (perhaps the 5770???). The processor is the AMD Phenom II X4 945 3.0GHz, and the RAM is 6GB DDR3 1600MHz (3 x 2GB). Thanks.