4850 Crossfire on this PSU?

A friend of mine is interested in buying another 4850 to run crossfire in his machine but is concerned about his PSU. He has a Corsair HX520 that has 3x 18A +12v rails.

Can anyone let me know if this will work?

Here is his card:http://www.newegg.com/Product/Product.aspx?Item=N82E16814127370

I think it's a tossup.I have the sapphire 4850 i just put in a new system.Most of these cards prefer 28 amps or more but my power supply only gives 20 amps(dedicated),but i have it set for combined amps which lets it go up to 80 amps combined.dedicated is how i should have it set up,but have'nt tried yet.

I would honestly suggest getting a bigger, higher quality power supply. Power supplies are getting cheaper these days and it’s not hard to find decent power supplies through cooler master, antec, and ext. Go 650w to be safe and he will do fine with 2 video cards, couple hard drives or optical drives in the mix.

What else is running in his system (CPU, RAM, etc...)? Is he currently OC'ing the system? Does he plan on adding anything past the extra video card?

It may work just fine, but as others have mentioned he would be better off with a bigger PSU. It would be a shame to drop the coin on the video card only to have it blue screen while gaming or limit his OC due to a weak PSU. It also may work for the time being but come back to haunt him when upgrading other parts of the system.

Side Note: I ran a Thermaltake 430W PSU with my HD 4850 in my HTPC rig for a short while. It ran perfectly fine with the system stock, but after slightly OC'ing the card and CPU it would blue screen randomly while gaming. I had no room for improvement so I swapped for a larger PSU and the system drastically improved. Higher OCs and the system was 100% more stable. It's always better to have more power than needed than to be starved of it.