I was going to say 2H, because that's my favorite, but there are quite a few good IPA's out there. If you are going to buy a kit, either 2H or Ruination would be good.
Otherwise, I recommend checking out the recipe section, go to the American Pale Ale category and sorting by ranking. Look them over and read comments.
I've made the 2H recipe on here and it was very close.
You might also consider one of the house recipes from some of the HBT frequenters.