actually why im not recommending 2X R7 260X bec,
its not a powerful GPU to xfire.
You will get only a less performance advantage in doing it.
heavy power consumption/heat compared to a single card.
not worth the price. if 1 GPU comes around minimum 110$ 2X = 220$ in that you can even get a R9 280.
if you are willing to spend for fx 8350 & xfire r7 260x.
get a FX 8350 & R9 280(worth for your money) & it will be a very good gaming PC.