Buy a cheap wattage tester, basically a pass through that goes on the plug. You be able to see if you are starting to reach the limits of the psu that way.
Heres a nice one:
http://www.newegg.com/Product/Product.aspx?Item=N82E16811990009
Or a little more nice:
http://www.newegg.com/Product/Product.aspx?Item=N82E16811992005
Questions
Why not 3 GPU's? Did they not fit?
How is the Corsair Link? Is it worth it?
Anyway's the cable management is insane. Makes me want to get custom cables now.
If it is not out of stock on the website you ordered from then it should be fine. But make sure it didn't say back ordered. If it was backordered then it could be a while before you end up getting your motherboard.