[abhijit_reddevil]

Well, you can get Leadtek WinFast PX6200 TD: 128 MB, 128-bit, chip running at 300 MHz, memory running at 550 MHz, PCI Express. This was explained a few posts earlier in this thread itself. And please make sure that it is a 128-bit one and not having turbocache memory but having it's own memory. This should come within your budget and compatible with your motherboard (915 chipset) which has a PCI-express slot.

This should come within your budget. I am not sure of the price of 6600 with both DDR and DDR2 memory. So I am not recommending that. But it will be definitely better than 6200. But it should be priced a shade over 6500 for a 256MB version.