Will this power supply work?



PSU is plenty for your system. Could run that system off of 550w, with overclocking. It's a great choice for a PSU, too - Seasonic are the best in the business.

 
Solution


Having 2 12V rails isn't a problem. It only starts getting worrying when there are multiple rails. Seasonic are a great manufacturer, and wouldn't hesitate to buy from them :)
 
Don't be misled by what's shown on the label. That power supply only has a single +12V rail rated at 48 Amps. There is no multirail overcurrent protection on those rails. If it really had two +12V rails then each +12V rail would have its own current limiter.