When ya start swapping turbos, keep a spare stash of money around... especially if its a daily driver. A lot of people say if you do a turbo swap you should have enough cash on hand to replace the short block if needed. Of course, depends on the driving habits.
No offense to your wife at all, but this is one of those cars that might be valuable to understand HOW it works under the hood... just not IF it works. Especially if you start pushing it power wise.
I'd look into a "stage 2" tune - turbo back exhaust and a tune. You can get "off the shelf" tunes for it. Look into a used access port or maybe open source tuning. After that maybe she'd enjoy some suspension mods instead. Power becomes pretty expensive after "stage 2"
In the mean time, kill some time reading these. Excellent info on both pertaining to just imprezas:
I'm sure she'll love it =)