As a rule, superchargers and turbos are a great equalizer. And yes, with a stock head they can achieve some pretty amazing things, but you can only blow so much air thru a straw as well, either with your mouth or an air hose. The first few psi of boost with really seem impressive, so will the next 1 or 2, but soon you will hit a wall where the more boost you throw at it, it really doesn't seem to make more power or gain. The stock head will help you while you transition to the better cylinder head, but it will have limitations as well, unfortunately, it will likely be much lower than what your expectations are wanting them to be. I would at least put larger valves in the stock head, and remove the bolt bosses, even if you don't install lumps at this point, that should be easy and cheap enough to do right now.
