which power adapter to use for my 8800gt

[jjj807]

Just got my 8800gt and have been playing AoC, wow game looks great. Anyway, I have my 6 pci-e connector plugged into the back. While reading the manual, it said for additional power to plug the 4 pin polex into the motherboard where i have a slot that says pci-16e, and the 6pcie dongle into the card. Which method is more efficient? Or are both needed? Right now im just plugging the psu pci-express adapter into the card, no need for the other one right? Thanks just checking dont want to blow up my new card.

ps. its an evga 8800gt