The next best thing you could do is get yourself an SSD drive. It will reduce loading times/boot times of your computer and all of it's apps/games (as long as they reside on it).
I reccomend the Crucial M4 or Samsung 830 - 128GB is decent enough for your OS + few apps + a few games. Should be around 1$/gig possibly less if you find it on sale.
I can't really reccomend anything else for your computer - as it is already a decent mid range system.
That evo cooler would be somewhat useless to you as you cannot overclock your computer - although it would definitely give lower temperatures. But IMO it would be a worthless upgrade for you.