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6600gt is slightly better, but usually slightly more expensive. The 6600gt falls between the x700pro and the x700xt. I don't know what brand you should get I got the Jaton 6600gt off newegg because it was cheapest, but I kind of wish I had gotten a name brand like msi, gigabyte, asus, etc. The msi has the best rating on Newegg now. I don't have experience with msi, but they must be rated good for some reason.