The best is Riva Tuner. Get the latest version. Just go up by 10's and if you start to see artifacting then shut off the game right away by Alt Tab and you can lower your settings. Remember to put your fan up to about 85 - 100 % to be safe. Your core is more flexible but your Memory will be a little more touchy. I had the EVGA 8800GT Superclocked and I got mine up to core 700 and mem I forgot. It was up by 50 though.