Your PSU is a bit overkill for the build. Unless you plan on Crossfire, you can use a 500W easy.
A few options: http://www.newegg.com/Product/Product.aspx?Item=N82E16817151093
I recommend this one, quality PSU, right size, and right price, plus it's modular!http://www.newegg.com/Product/Product.aspx?Item=N82E16817151096
(Along the same lines as above, but a little more power, it will supply )
edit: Saw that you were a 'maybe' for crossfire. If you think you want to crossfire, and want to budget for it now, the second PSU (Seasonic 620W) is a better choice than the OCZ because it's got more 12V output (combined 576W and 24A max/rail, versus the OCZ's 552W and 25A max/rail), and it will be a higher quality supply overall. However, I would consider going for this if your sure about doing crossfire http://www.newegg.com/Product/Product.aspx?Item=N82E16817151107.
The 620W is probably fine, and is better than the OCZ 700W, but the Seasonic 750W will definitely be solid for two 7850s.