While the corsair is very high quality and might handle it... GTX 285s are beasts. I would recommend you go higher.
The Corsair PSU calculator suggests 950-1000w. Its rather conservative, so I think you would be ok with the 850w model--but I wouldnt go lower.
Edit: Give yourself some wiggle room--especially if you plan to overclock anything. A stronger PSU will run more efficiently and cooler than one running near peak load.
This is on a mock system, but might offer some perspective as to just how much power you will use in relation to other setups:
...with this system it may actually be economical to get a silver/gold certified supply--you might make the money back on your electric bill. Seasonic, Antec, PC Power and Cooling, and OCZ also make some very good high-wattage power supples you could look at.