Yes, 5570 is the best you can get with your power supply.
p/s: I know this is off topic but can we put 2.1 graphic card in PCI-E 1.1? Just asking.
There have been issues with that setup, some board manufacturers fixed it with a BIOS update for some of their products but not nearly all. So the safe bet is if you have a version 1.x slot on your board then stay away from a 2.1 card.