Lets straighten some things out first. Power requirements listed for cards are actually for the whole system so they are referring to the combined power between the 12 V rails. Your EA500D has 2 12 V rails with 22 A limits on each one and 444 W (37 A) available between the two of them, its that 37 A number that is important. The EA500D can run pretty much any single card, i wouldn't run a GTX 480 on it, but something like a 560 Ti or a 6950 are well within its capabilities.