It has ~56A on the 12V rail(s). Thats probably enough to handle the 5850 CF'd. Not sure about their stealth line. You might want to research that a bit to make sure its a good one.
Look at the label again, it's 56a combined on the 3.3v, 5v, and 12v rails. There's no 12v only rating on it.
The OCZ SteathXStream's are basically re-badged FSP Eplisons/Everests which have wildly variable quality. You might get a good one but then again you might not. Personally, I wouldn't take the risk.