I have some advice here. I have a 96 impreza outback with the ej22 with 201,700 miles or so on it right now and it has a decent exhaust on it which sounds great! But, I need more power as well maybe 40 - 50 hp. What I want to do is do a hybrid, ej25 short block and 98 impreza 2.2 heads and intake manifold then get some delta 220 cams for the heads. It already has a lighter flywheel which is nice. I am expecting around 175-180 hp or so with an updated exhaust which will be about what I need for a while for my wagon. Another thing is tranny swaps to like a 99-2001 rs 4.11 tranny. Our cars have the 3.9 but the 4.11 final drive will have just a bit more torqyness than the 3.9.
So, you really have to think about the money to added power thing and decide if these few things will get you what you want for now or saving money for a stock wrx and then going from there.