I don't know, you could get lucky with a those parts... but I'm not sure Subaru was all that conservative when they first tuned the 2.5 N/A engine.
As far as exhaust, go with a set of Borla replica headers from eBay, and then snag an Impreza cat-back to go with it. As far as intakes, there aren't too many out there for your application. Just about any intake for the 2.5RS Impreza (USDM 99-01) will work though.
Stay away from "chips" though, they're a joke when it comes to imports... and more often then not, the same reigns true with domestics.
See if you can get a local shop to do a custom tune for you, I believe there are some Subaru specialists in your area. Worst case, you could swap to the MY99 2.5RS ecu and get a custom tune since I'm pretty sure they will accept new tunes. I'm not sure the Forester ecu was reprogrammable for that model year.
Also, you should look into some other items to help reach your goals. You could get cams which would almost guarantee those numbers if you pick the right ones, but getting some intake and throttle body spacers will help a bit. Also swapping out for lighter pulleys will help you net some more power to the wheels at least.
there is some good reading in the 2.5NA subforum, as well as over on rs25.com
- 200 HP from a 2.5 n/a with just bolt ons?? - Subaru Impreza GC8 & RS Forum & Community: RS25.com