If you've read enough threads, you'll also realize that questions are always pertaining to what your going to use the car for? What your end goal is with the car? Te reasons....so there is a basis to work off of and not recommend something that you'll be paying twice for it later down the road.
If you want the car to start reliably everyday, not have any sort of hiccups, not worry about it...leave it completely stock and make sure it's a stock map in the car...having a dowpipe and a CAI would make that car run a bit off on a stock map.
Since there is naturally maint. required on a car, especially of that age and possibly higher mileage, make sure your spending the money where it needs to be put. Maintenance is the most crucial aspect of a Subaru, well, any performance oriented or vehicle that will see some spirited driving.
1500 cap, there are more than a few things you can do, higher ticket items to allow for huge and massive power gains, not so much, but starting to get yourself in that direction with porting of the intake, exhaust manifolds, TGV deletes, electronic boost control solenoid and what not is a start.
You may also want to get the turbo looked at to ensure that it's in proper working order, turbo inlet for tears, and maint. service intervals to be performed (fluids, plugs, belts inspection for brakes, suspension and what not) and things of that nature. Remember, some years there is nearly 2.50 a mile in maint. costs.