Zalman 850W enough for 2xgtx260 SLI (super overclocked version though)

Afternoon,

I'm currently running a Gigabyte GTX260 Super overclock in my system which already is a power hungry beast and at the moment has been serving me pretty well, easily beating a baseline gtx275.

My PSU is;
Zalman ZM850-HP Heatpipe Cooled 850W Modular Power Supply

Other specs;
Core i7 920 oc'd to 3.67ghz
3gb ddr3
4 sata hdd's
1 sata dvdrw

I'm also quite pleased with the PSU, it being effecient and so far excellent quality.

Would it be capable of running 2xgtx 260 "super overclock" ?? My thoughts are yes, but instability through power issues gives me the fear.

Cheers