Replacing power supply.?

So I am thinking about replacing my power supply. I have a Dell Dimension 4700 (a href="http://support.dell.com/support/edocs/systems/dim4700/sm/specs.htm#wp1043338)" rel="nofollow"http://support.dell.com/support/edocs/sy…/a but I know little to nothing about these things. Is there a requirement for a power supply? If so, could I use this one a href="http://simtechs.com/product/powerSupplies/ps-atx-480-BlkBeauty.html" rel="nofollow"http://simtechs.com/product/powerSupplie…/a ?