That swap will eat your budget really quickly. Will you be doing the work yourself? Are you going to merge the harnesses together?

High 200's will need intercooler, injectors, turbo, downpipe. exhaust, and uppipe upgrades. So that's maybe another $1500 on top of your budget NOT including tuning.

There are RS's with wrx swaps for sale in the 9k range on rs25.com that'll save you a lot of work/money.