If it's the Enermax Infiniti 720W, then it's way more than enough, you did good choosing that one. And the 8800GTX needs 2 additional PCI-E (6 pin) power cables aside from the power that is provided by the PCI-E 16x slot, but don't worry the Enermax Infiniti 720 comes with 3 additional PCI-E cables, so you're covered.
Dude, your PSU could power a rocket if you actually set your mind to it. I'm pretty sure your GTX brings a 2-Molex-to-PCIe cable (I know my 8800GTS did even though I don't use it), so with one of those cables and the other 3 PCI-E that are on the PSU you are pretty much covered.
Molex= 4pin for fans and optical drives.
EDIT: in case you're wondering, I mean one of these: