Assuming you have not got a JDM import with the 2.0 twin scroll and you have a 2.5 currently you should be on 296 tehn with what you plan that takes you into the PPP / 330s area which gives circa 330bhp.
Now I had no issues running 330 bhp in my first STI hatch however you will read many tales of unfortunate ringland failure. A decent map will go a long way to ensuring this does not happen as it will ensure No 4 pot does not run lean at the higher revs. Budget in the future to replace the pistons with forged items, also look at a timing belt kit funds (due at 40K)
A cheaper mod is the cylinder cooling pipe discussed on another thread - this, allegedly will help a lot with the heat on No4 pot which will also contribute to ringland failure. I will be completing this work as part of my re installation.
https://www.blingstrom.com/modmonday-sti/2019/3/17/getadomtune-cylinder-4-cooling-mod-showing-cylinder-4-that-you-still-care
https://www.iagperformance.com/GDT-Cylinder-4-Chamber-Cooling-System-WRX-STI-p/gdt-1005.htm