... sigh, and how many people who know how to use this product have not been able to purchase it yet? lol
Anywho, yes, the 6+2pin connector will serve as your 8pin, and then the 6pin connector will go in the other slot. More important than the connectors is the power rating, and the quality of power supply (bigger is not always better, nor is it always adequate). But assuming it is a quality power supply, and meets the requirements set by nVidia on their site, then you should be good to go.