btw, HD 4870 is way powerful than a GTS 250, and the 4870 512 is just around 7.5k though power consumption is bit on the higher side, and the idle power consumption too is on higher side, if u dun flash its bios to lower clocks and voltages while idling. 512 is enough, as 1G makes only 5~6% diff. Check guru3d comparion on 4870 512 vs 1G, and even at 1920*1200. diff is negligible.
Next is HD 5770. Its slightly slower than 4870, but is DX 11 and consumes much lower power, and greater room for OC, but on the downside, it costs more about 9.5k for the 1G version.
The best performing ATI sub 11k card is the HD 4890. It is almost 11k, but much powerful than all of these cards, but consumes power like hell compared to HD 5770/GTS 250.
4850<GTS 250<HD 5750<HD 5770< HD 4870< HD 4890< HD 5830< HD 5850.