Opening up your exhaust will definatly help plus opening up the air passages will benefit for sure.....I would make guess around 345-360rwhp....or so...
So your car is basically stock with gears and supercharger and the mods for a proper supercharger running. Your on the right path, no doubt but your engine is really stock.
I don't know if the Street heat intake would be the best choice, I would go the extra mile and get the Track heat if I were to go with TFS. I know a guy that is selling a Street heat for a good price, contact me if you want his contact info. He also has a 75mm Accufab TB for sale for cheap.
If your going to go with exaust, go the right way. Do longtubes. They are a little more hard to install but worth it both for power and sound.
It's still going to be hard to get 400rwhp with stock heads, even with boost. If you can't afford them too, while you are in there take them off and do a little porting on them, that will make a good improvement.