Due to the fact that computer use much more from the 12 volt rails these days, that power supply is a big no go for a new card.
That said, if they made a power supply with that many amps on the 12 volt rail, it would generally be a 250-300 watt unit.
Not that the unit can not claim to be a 500 watt psu, just that most power supplies now channel 80%+ or there power into the 12 volt rail(s).
Also new designs get there 5 and 3.3 volt rails off the 12 volt allowing lots of 12 volt power(current) while 5 and 3.3 volt usage is low.
Once loaded the card will be able to take nearly ALL the power from the power supplies 12 volt rail, not leaving enough for the rest of the system.
To sum it up, your power supply has 216(150-200 of that will be used in heavy gaming) watts on its 12 volt rail and the Corsair unit linked above has 480watts on its 12 volt rail(450 if you somehow manage to load the 3.3 and 5 volt rails to the max, but thats not going to happen).
I would not risk the system on that psu, and i am the one running a 300 watt psu for my I5 750 + 5770 video card