Is an Antec CP-850 enough for two HD6950's

When I built my rig last fall, I decided to go with an 850W PSU thinking it'd be enough to run two cards in xfire, but now I am starting to worry, lol. I am going to be upgrading to a 6950, and after I sell my old cards (a 6870 and a 5770) I think I want to get a second 6950. Should I look at getting a bigger PSU?

My full system specs:
Gigabyte GA-890FXA-UD5
AMD Phenom II x6 1055T (I haven't tried to oc yet, this would be my first so I'm still a little worried)
Corsair H50 cooler
2X2GB Corsair Dominator (will be upgrading that to 4x2GB at the same time I get the first 6950)
2 HDD
1 DVD RW
Everything is in an Antec 1200

I've plugged everything into the extreme.outervision.com/psucalculatorlite.jsp calculator, and is says I only need 550 watts, but I figure it's a good idea to ask here before I get in over my head, lol.

Easily. In the 2500K rig in my sig with similar setup (I probably have more fans, my pump probably takes more power too) I pull at MAX 550w from the wall with CPU at 5GHz and cards at 950/1450 (flashed to 6970 and OCed)

No issues with CM Silent Pro M 850w. Normal gaming load ~330w.

Awesome! I was hoping that my PSU would be able to handle everything. I got kind of worried when neweggs PSU calculator suggested I need at least 880W, but I think I remember reading somewhere that that one was inaccurate.