What's the best PCI or AGP video card for gaming that only requires a 250 Watt Power Supply?

I have a Compaq 5311SR and it has a 250 Watt Power Supply and a Ati 9550. I don't want to buy a new Power Supply|||To the person above. A 250W PSU is not enough for an 8800 GTX . I would think that a Geforce 7600GS or GT could run on 250. However I am not 100% sure. This would depend on how much power the other parts of your computer and any other devices (such as something plugged into a USB port) use.|||Don't know about power, but for a card try nVidia 8800 GTX