I have heard, no hard data personally, the stocker is taxed/stressed at 50 PSI. Try a search on this site maybe it'll pull up. I can't search well for whatever reason.
As for stock vs aftermarket IC's or water to air. Look at the pressure drops and efficiency between the stocker and some of the aftermarket coolers.
IIRC- stocker is 3-4%? Some of the aftermarket air to air are 1-2%, simply easier to push the air through it. The other part of the puzzle is how well they cool the air, this is a percentage based number as well.
When in doubt... use the coldest medium to cool the air and reduce as many bends as possible reducing friction heat, keeping air speed up. The more you bend, the bigger the pipe.
IMO- the IC is one of the small expensive parts on the list of improvements. PErhaps, if you use N2O, you could spray pre cooler to offset some spike? Guessing here.
Good luck with the build!!