if you don't mind paying for shipping, i would get this power supply unit
It has 700 watts is crossfire ready and is modular so you can remove any unwanted cables that you aren't currently using.
With the new Power supply, it lets you use a different Graphics Card whom you can still crossfire elater on. The one you posted anyway doesn't take advantage of your motherboards SLi and is overpriced.
if you spend 15 dollars more, you get a free game and about 3 times the performance of the card you posted. And you can also crossfire this later on.