What will the other one be?
In most cases, these power supply calculators are pretty accurate, though ones from a vendor (in this case, Antec) will be weighted to side on the power heavy side so that you buy an upgrade.
That being said, the Antec one you just linked is amazingly accurate for what it is. I'm adding that one to my favorites (thanks!)
Depending on usage, and what your other card is, my knowledge and experience says as long as it's not another video card, or at least, a low powered video card, you should be fine. full system specs though would help us gauge your needs better.