Couldn't agree more with RCZ, the analysis used by Corky was over simplified in order for the somewhat average reader to not struggle trying to figure out what's being said, which is why the numbers came out so inflated. The conclusion is still the same, an intercooler will yield more HP at the same Boost Pressure in the end.
If you want to get technical however, nothing beats experimental analysis. Number's from the real world. Here's a nice read:
Understanding Intercooler Efficiency and Pressure Loss - bimmerfest - BMW Forums