I need to replace my power supply on my desktop computer, not sure what to get?

I have an (http://www.newegg.com/Product/Product.aspx?Item=N82E16811144205) and the power supply crapped out, the fan hardly spins at all. The power supply is (http://www.xoxide.com/sunbeam-casegears-hush-580w.html). Apparently this model of power supply is a piece of crap, I want to get a better power supply but I'm not sure how to find one that will fit in the computer I have.