My most common thoughts:
- moroso pickup and stock pan. Way less $ for something that won't see competition.
- intercooler?
- tuner can recommend which fuel pump they like
- arp head studs. Drop in solution.
- "The right stuff" for Subaru gray bond substitute or whatever. Readily available, comes in cheez whiz can for easy application
- Engine gasket set. Buy for your heads. For reasons related only to availability of rebuildable heads, I used D25 heads for my 2005 car. I bought the gasket set for the 2011 wrx I used heads from. Maybe you can pick and choose which gaskets you need individually, though that gets super time consuming.
Thinking about your budget now as my mind goes to "while you're in there" town.
Maybe do a compression and leak down test on the current block. I can see spending $4k on block, turbo, heads, tune and fluid damper. See what you can reuse.