A single video card with the exta 6 or 8 pin connector allows it to draw power from two sources , the 6 or 8 pin connector and the Pci-e slot. So it will get the required amps as a total from those two sources.
The psu is enouigh for the video card and the rest of the sysrem that you have. You could have gotten a better psu but you have what you have and it wil suffice.
Don't forget that you have to take into account the efficiency of the psu and that's why they have the Bronze , Silver , Gold and Platinum cretifiactions on the psu's.
You also want to know your psu's continuous rated power and not the burst power. Your psu might say 700w but will it sustain that rated power or will it just give that in a burst mode and the continuous rated power being lower.