Correct me if I'm wrong, but are the IBU's predicted by BeerSmith something to take with a grain of salt? I can't imagine drinking a "Pale Ale" with ~125 IBUs. That sounds disgusting for me, and I like DIPA's.
The ceiling for what your palate can pick up is generally quoted at 60-70 IBU's. And the ceiling for IBU's in a finished beer is somewhere in the 100 IBU ballpark. The equations used to determine IBU's are merely tools for estimates. At best they will get you in a ballpark, and then you can tailor the recipe once you have "calibrated" it to your software, system and palate.
For example, I brewed an IPA this summer that my software calculated to be almost 400 IBU's. I sent it out for lab analysis and it came back at 98 IBU's. Flavorwise, it tasted like 60 IBU's, but with a rather smooth bitterness. Just because your software estimates 125 IBU's, that doesn't guarantee that it will be a gross beer. It will probably be an IPA rather than a Pale Ale, though.