Best graphics card on a 500w power supply?

Solution
Although HardwareSecrets found a number of Rocketfish PSUs that burned well under their labelled rating, that appears to be a newer one. I confirmed on 80plus.org that it is 80+ certified, which means it was tested at 100% of its label. You could safely run a HD7870 or even a HD7950 on it.
As DavidY just said, it depends on the quality of the "500W" PSU. If it is truly capable of 500W (e.g. a Seasonic, Antec, or Corsair), you could run a HD7950 or GTX570 on it. If it is a CM, Logisys, Apevia, or Diablotek, the label is a lie, and it is probably capable of no more than 430W (CM) or 300W (the others). On the CM, you'd be able to run a HD7770. On the others, nothing more than a HD7750.
 
Although HardwareSecrets found a number of Rocketfish PSUs that burned well under their labelled rating, that appears to be a newer one. I confirmed on 80plus.org that it is 80+ certified, which means it was tested at 100% of its label. You could safely run a HD7870 or even a HD7950 on it.
 
Solution

Yeah that seems to be the general opinion. While some Rocketfish can be janky this one has rather nice reviews. I've been running it for a year with no problems. I'll probably go with the Radeon 7950.
 


I know right? I believe I price matched it and got it for like $100, and that was a year ago. Still, could have gone a lot cheaper. But I got major discounts on the rest of the lot so I'm not too fussed 😛