600 watts enough?



It's more than enough, I would recommend this one: http://www.newegg.com/Product/Product.aspx?Item=N82E16817207013&Tpk=xfx%20550w&IsVirtualParent=1 or http://www.newegg.com/Product/Product.aspx?Item=N82E16817139027 or http://www.newegg.com/Product/Product.aspx?Item=N82E16817139026&Tpk=cx430&IsVirtualParent=1
Your card and system will pull around 250w at load with a 3960x. http://www.legitreviews.com/article/1863/12/
 


Then you would need a little more power, and a better motherboard, the 970 can not Crossfire reliably.
You need a 990x/990FX board for multi GPUs.
Also, xfire on mid range GPUs are a bad idea at the moment. Lets hope AMD fixes their drivers issues at some stage.
 
Already bought my MotherBoard :/

 


Then multiple graphics cards are out the question unfortunately...