One last bit of information just to place at your fingertips...

The stated specifications for power usage are as follows:

450 Watt or greater power supply
with a minimum of 24 amps
on the +12 volt rail.

The above stats are actually right off the box of the EVGA 01G-P3-1373-AR .

I have the card and am putting it in a machine in the next 48 hours.

Sorry, you will have to check on the other cards specifications as I don't have those at 'my' fingertips.

Lastly, I want to mention that we all know that the "24 amps on the +12 volt rail" matters just as much as the number of watts a psu has at its disposal.

So in the end it all depends on what else your system is running but I would be confident running a quality 650 Watt psu with requisite amps per appropriate rail if your box isn't packed to the gills.

Grail