No need for another PSU if you have an Epsilon 600w PPA6000113...
According to the BFG spec sheet click here, you need a 425w or better PSU with a combined 12V current of 28A or more.
Don't these cards draw their power from 2x 4-pin molex to 1x 6pin PCI-E connector? In this config, I'm not sure if the Amps double to 36, but I'm sure your Epsilon will be able to handle it with ease if connected as above. G
P.S. There are others who run a 8800GTX on that PSU click here & click here. I've also read about people using & mere 460W PSU (this case+PSU combo click here) to power a 8800GT
Your power supply may work, the card requires a combined 12V current rating of 28A or more. You would add the 12v numbers together to find out the maximum amperage supported. As long as those two numbers add up to more than 26, that power supply should be fine to power this card.