I'm buying a GTX 680 GPU and concerned that my Seasonic 700 Watt modular supply will be sufficient. Nvidea says 550 W is enough but I tend to be skeptical of performance claims. Another concern is the cables and connectors. The GTX 680 requires an 8-pin PCI-E connector, which I have (actually it's a six-pin male to 6 plus 2 pin male). But the PSU outputs accept only 6-pin connectors. I don't understand the logic of a 6-pin output feeding an 8-pin GPU input. Should I use two separate outputs...a 6-pin and 2-pin? Thanks.
Usually the graphics card manufacturer puts down more watts than it actually needs, to deal with different manufacturers, different psu's, capacitor aging, etc. You have a good enough power supply. You can use thermaltakes power supply calculator if you are really nervous. I would not use the adapter they give you for the graphics card, I would use the 6+2 Pcie connector directly on your power suppl. The adapter is for PSU's that don't have the connectors but meet the requirements, which are usually older ones.