Or you can really bust out the money and buy this thing: http://www.newegg.com/Product/Product.aspx?Item=N82E168...
It's like the king of PSU's you'd have it forever, you could probably be buried with it. Seriously though, a 750w would run two of those cards well, but it's nice to have a big space between what your machine needs for power and what your unit can safely deliver.
i have the OCZ that you mentioned there, I got it on sale at NCIX a few months ago for $90 so I couldn't pass it up. However, Corsair is a more reputable brand so if the prices are comparable then I'd go with the Corsair..
now back to your wattage, you do realize that PSUs take a big nose dive in efficiency when below 20% load. and at idle, where your rig will mostly be at, i cannot see more than 150 watts being used. so after you spend $200 for a silver/gold rated PSU; you will be getting the efficiency of a 80+ rated . . . not even bronze.
take a look at the "low load" tests in each review . .80% and 81%
edit: you can spend half the amount for a quality bronze 750 watt psu and have $100 towards another 7970.