I just wanna chip in with a quick tidbit.. These PSU's seem incredibly well made, mine is running almost 24/7 crunching/folding/gaming, varying between 650-820W measured at the wall depending on gpu clocks, and even seen up to 900W when running firestrike. I guess that's still around 800W when you factor in efficiency, but what impresses me is how the thing never really gets warm at all, the fan doesn't even spin up much either. I'd recommend the OP get a wattmeter so you can see what's going on, but I don't think that 850W psu is going to have any problems at all, the rating seems very conservative.