I want to upgrade my pc's GPU. I currently have a Radeon HD 6670, AMD Phenom II X6 1055T Thuban 2.8GHz a 430 watt psu and ASUS M4A88TD-V EVO/USB3 - AM3 - AMD 880G. I want to upgrade to game. My price range is about 500 to upgrade. what would be a good GPU to get and does anything else need upgrading. thanks