[Build Help] Can my 850w power supply handle another GTX 480?

I know that you guys are the ones to turn to with a tricky question like this. I've been running the same Thermaltake 850w power supply for my last two builds: http://www.newegg.com/Product/Product.aspx?Item=N82E16817153043

It started on a Q9550/GTX 285 build and now it's running my new build from last summer:

• Coolermaster Cosmos S Full tower case

• EVGA X58 3-way SLI Intel Motherboard (on fire with blown capacitor[since replaced, thanks EVGA!])

• Intel i7 930 2.66ghz overclocked to 3.5ghz with Corsair H50 water cooler (possibly also on fire)

• 6GB Mushkin DDR3 RAM, 6-8-6-24 1600mhz

• EVGA GTX 480 graphics card

• Creative X-Fi Titanium PCI Express sound card

• Intel X25-M 80GB Solid State hard drive

• 2x 640GB Western Digital Black Edition hard drive

• 2x WD 500GB server hard drives in a RAID 1 backup array

• 1TB WD Black hard drive for DSLR photo/video storage

I'm on a tight budget but my GTX 480 is currently being straining by some of the stuff I'm trying to get it to do (BF3 all Ultra at 1920x1080 60fps while recording with dxtory). Used GTX 480's are coming down in price and I'm wondering if I could buy a second one and my power supply won't die a horrible death. A friend is running a 5.0ghz OC'd 2600k i7 with two GTX 580's in SLI, but both his i7 and the 580's are more power efficient than my i7 and 480 so I'm skeptical.