XFX 850W Black Edition Power Supply Enough

This is my current build:

ASUS Rampage III Formula - Intel Core i7-950 O.C. - 3.3
Antec Kuhler H2O 920
G.SKILL Ripjaw 12GB (3x4GB) 1600MHz
ASUS GTX-580 DCII
OCZ Vertex 3 - 120 GB SSD
Seagate Barracuda 750 GB
XFX 850W Black Edition
Antec P280
Windows 7 Home Premium 64 SP1

I just recently purchased another ASUS GTX-580 DCII to run in SLI. I have the original XFX 850W Black Edition Power Supply which is made by SeaSonic. I want to know if I am going to be okay with this set-up as is. Or should I invest in a new higher watt power supply? (Either SeaSonic X-1050 Gold or SeaSonic 1000 Platinum)

I have a slight overclock on my CPU to 3.3. I do not plan on overclocking the graphics cards since they should be enough power to handle anything I throw at it. And at this point I do not see the need to increase the CPU OC either. I haven't had a single issue with the power supply so I would prefer not to replace it.

Let me know what you think. Thanks.