try overclocking with the find max..
i have an x700, and my core does 490 mhz stock cooling, yet it actually performs worser at 490, so i got core to 480 and memory all the way up to 550 max, backed it down to 540 x 2 = 1.08 ghz.. works fine. got 1,500 points more in 3dmark03 from it