I like both units in that combo. I don't think that you will use all 950 watts, (unless you are planning on sli) but it looks like it still is pretty efficient in the range I think you'll be using it in.
Try putting the build through the newegg power supply calculator It all depends on the cards you are using, and you have to remember to look for enough 12 V current. What is enough? I'd have to look, but to start out look for a supply which spreads the gfx connectors out across multiple virtual rails, or doesn't split the main 12V rail.