ExtremeTech just published a shoutout which may help you. They take a look at four $320 graphics cards and three graphics card in the sub-$250 range.
The three cards priced below $250 are the ASUS EN8600GTS 320MB, the ASUS EN8600GTS TOP 320MB, and the AMD ATI Radeon X1950 Pro, the last of which is the only AMD card in this roundup. The first two are both based on the GeForce 8600 GTS chipset at 320MB.Check it out over here.
Meanwhile, four GeForce 8800 GTS 320MB cards are priced around $320. They are: The ASUS EN8800GTS, the BFG GeForce 8800 GTS OC, the MSI NX8800GTS, and the MSI NX8800GTS.