What's the needed power for a graphics card?

I’ve gone about the process of building a computer- I’ve picked out parts, and I’m just about ready to order.

One thing that worries me, however, is if my power supply will be sufficient for my graphics card. My PSU is rated at 350W and the power supply calculator states a recommended power of 304W, but I don’t have a clue about the 12V lines, what they mean, or if they are adequate.

I plan to use a Radeon HD 4850.

Here is the information:
+12VA / 12A +12VB / 18A
+5V / 18A +5Vaux / 2A
+3.3V / 17A -12V / 0.8A

Combined power of +12VA and +12VB is 300W.
Combined power of +5V and +3.3V is 160W.

Will this run my graphics card or should I buy a new one?