Recommended Watt number for GPU - Asus GTX570 DCII?

The card requires 550W brand PSU

http://www.legitreviews.com/article/1763/

i think it's an 550watts but your psu is enough for your system but not for overclocking anything if want OC then look at 750watts

Don't worry.. if your PSU have a full 12v wattage line (620w in them), it delivers 51A.
This is enough even for a GTX 590 with a heavily OClocked i7.

Don't need to get a beefier PSU.

Let me guess.. this PSU is Antec Earthwatts 620w?

I will give you more accurate answer:
The GTX570 no OC usues maximum wattage of 219W with means 18.25A needed for it only on the PSU's 12V rails.
The PSU Corsair VX550W has 41A on the 12V rails.
GTX570 max OC wattage is 394W - needs 32.8A on the 12V rails - that is 14.58A more.
So if you intend to fully OC the card you will need a PSU with 41+14.58=55.58A on the 12v rails, which tend to be in the 700-750W area.

already mention on my above post.

Actually this PSU is SeaSonic S12II 620w

Thanks to all of you guys..