Not a Subaru service.
Use the search button up top and look up Verso and Ecutek for prices and peoples experiences etc.
Dont expect any change from about $1200 for either for your first tune (re-tunes are cheaper later on).
My personal experience tell's me I will continue returning the ASG in Malaga for my future tuning. They will Verso tune your car.
OR you can go aftermarket
ECU such as VIPEC, MOTEC etc.
For a street car that barely/doesn' see the track, don't waste your money/don't let anyone talk you into wasting your money...
At the same time as the exhaust and tune, I would definitely upgrade the fuel pump and increase the boost slightly
To be honest whilst it's in the shop, possibly look at a turbo and intercooler upgrade as well to get a massive increase in performance.
If you you do the standard engine mods, definitely think about your suspension and brakes also. Thicker sway bars, upgraded brake rotors etc etc