I opted for the Gainward 4850, but I'm worried about actually putting into my case now. Both the box and the manual recommend a 500W power supply. If I absolutely must, I'll purchase another power supply, but only if such action is imperative.
Thanks for all the help, but I'm having trouble understanding something in the manual; I've never had a graphics card requiring external power. I thought it was a simple case of plugging in a spare 6-pin power connector, but I stumble across this: "Connect the female connector of the hard disk adapter cable to the power connector on the back of the graphics card. Then attach the male connector on the cable to matching connector from your computer's power supply."