Thanks, I checked that card and it says:
"500W (or greater) power supply with one 75W 6-pin PCI Express power connector recommended"
Are they just exaggerating for safety when they say 500W or greater?
And secondly, it doesn't matter that my PSU has two 12v rails right? Because I have read ambiguous things about this.
Those are the recommend ratings which the manufacturer plays very safe on. spentshells and I noticed you have a Seasonic PSU which is the top brand there is and you shouldn't have a problem running it.
I wouldn't go overclocking but you should be fine at stock speeds.