Best vs Best Bang for your buck?
As far as cooling charged air Process West makes some of the best cores I have ever seen. The weld lines are exceptional and their datasheets show solid improvements over stock coolers. That said unless your turbo is too large for a TMIC thats the way I would go, Shortening the piping and air path will reduce lag and you will still see a notable improvement over your stock TMIC with a process west drop in unit.
That said they arent cheap, if you want something less expensive with better performance than your stock cooler greddy makes a few big universal intercoolers, Just keep in mind the bigger you go the more turbo lag you get and there is a break even point where the benifit is scrubbed by the material in the way of the airflow.
If it were me and i had a grand to spend I would swap out the OEM top mnount with a process west top mount and protect it with a nice steel mesh screen ( bugs big enough to bend fins out here )
13 WRX Hatch