If you can weld and do your own fab work a turbo would be way cheaper than a big bore or any serious engine mods and would smoke a stock 750 all day!
I was looking into big bore, head work, and aftermarket cam for my 750 but I went turbo, I built it for way cheaper and if I blow it up I could just get a new motor and put the turbo set up on the new motor. Its a everyday bike around town or 800 mile road trip no problems. The power increase from the turbo is unreal and once you feel the boost kick in you will never own another bike with out one.