Wiesco just released a new line of rods for the turbo market (including Subies) rated to 1000hp. They make amazing pistons and you can order a custom set if you need. As mentioed by titter, you're still on a smail, and other basic mods are still waiting. I'll recommend you part ideas but before you go pricing them out we need you to read the FAQ made years ago about going 400whp on Nasioc found here
-ID1000cc, fuel pump, lines, rails (bigger rails flow more at same pressue, allowing inj to flow more at same IDC)
-EWG and header-back exhaust (catless isn't a necessity, more of a spool thing)
-Intake and intercooler (TMIC for spool/FMIC for another 20-30whp if you're moving)
-Bigger turbo (Blouch makes a great bolt on, the 1.5DOM XTR is designed around the 2.0L, comes single/twin scroll and is good for 380whp with 16g/18g spool) FYI bigger turbos spool later, so a 500whp turbo can spool so late you might get 1500RPMs of power if not done right. Sizing is key!
-EBCS (aids in spool and boost control)
There's a starting point, do research, ask questions, post thoughts. It's your build so do it for you!