What heatsink are you using right now? If it's a low-end air, then the H50 would help. If it's something pretty decent, then I would just keep it. You should be able to hit higher than 3.5 GHz with that e5200, though. The H50 also has the benefit of reducing the number of fans in your case by one, since its fan replaces the rear exhaust (just something to keep in mind).