I think you would see more of an instant short term performance gain from the exhaust, but the intercoolers are a good buy if you live in a hot place, like to drive hard or go to the track, or plan on upgrading turbos in the future.

Because colder air is more dense if the intercoolers lower IAT's substantially (depends on situation) you could "free up" horsepower and get a little gain, and also help keep it down on repeated runs so you dont get bad heatsoak. But im pretty sure a catback with your chip would give you more power, plus the sound of an aftermarket exhaust is goooood.

 

Oh and while K04's are bigger than K03's they arent really massive, how about dual garrett GT30's