Your stock airbox is already a "cold air" intake...it pulls air from outside the vehicle via the space behind the passenger side headlight. KKM, drilled airboxes, etc are not cold air intakes....they pull hot air from under your hood.
That being said, most people who have done those mods are happy with the result and felt like they gained something. I noticed a bit of a MPG gain from just using a drop in K&N filter in the stock airbox.