If you haven't done a fresh install, I would recommend that just to rule out any software related slowdowns that have piled up over the years. If you don't have an ssd, that would be the first upgrade. They are relatively cheap for a 240gb and can be re-used if you want to replace other components. Replacing a mobo adds no performance or really any benefit at all. That was the last gen for that socket so there is nothing more you can do without replacing both cpu and mobo at once. Depending on what is slow would determine what you should upgrade but you are lacking info. My 2500k rig is still fast enough for almost everything so a 3770k would have no issues besides getting into the higher end of things. Of course it's overclocked but with that combo, I'd assume you would be too.