I have a slightly different take . . .
For street driving, torque is far more important (and usable) than HP. But for a number, 325 ft*lbs @ 4250 rpm computes to about 263 HP (I'm using the 2010 production number that also apply to the FRPP tune for earlier S197s). Maybe round that up to 300 to cover occasionally running the revs out to 5000. And honestly, while it would have been nice if Ford had built another 75 HP into the 4.6, 300-ish is plenty for the street.
So far, I'm mostly good with 325-ish HP even when I'm out on a road course. I know I could handle quite a bit more than that (and have driven cars on the track that had considerably more), but I don't have to have more in order to enjoy the day.
Maybe when your focus is on the corners rather than the straights, power takes a back seat and it becomes more about getting the most out of how much power you do have. IOW, more about you and your driving and less about the car and its engine.
Norm