That is a decent power supply. I saw CoolerMaster and had to find a review because they do not really have a reputation for quality power supplies but that one is good.
http://www.hardwaresecrets.com/article/Cooler-Master-Silent-Pro-M-850-W-Power-Supply-Review/810/10
Most people think they need way more power than they actually do. As manufacturing processes get smaller parts use less power. So a newer CPU or graphics card actually uses less power than one a few generations old. Also most of a modern computer's power is from the 12v rail of the power supply. That's why you see people referencing the 12v rail in so many power supply discussions.
A good quality power supply will actually be underated. A cheap power supply ( and some expensive ones ) will have a hard time delivering the rated power and will have alot of noise and ripple so the power it's supplying is not "clean". This can damage components. So you should really research before buying. Jonnyguru and Hardwaresecrets are about the two best review sites on the net. This is a good list too, not perfect but a good place to start.
http://www.eggxpert.com/forums/thread/323050.aspx
Dell usually uses decent power supplies that can pull the rated wattage.
AMD and Nvidia both expect you to have a low end power supply when they recommend how much power you need for a certain card. All you really need to pay attention to is amps.