For my MY99/00 WRX, I came across an opportunity to pick up an engine with the EJ207 block (semi-closed deck and forged pistons) but with WRX heads. Previous owner did what you are considering. In my case, they spent all the money, and I scored a bargain.

With a VF48 turbo and BP98, it makes 250HP at the wheels (roller dyno), and pulls like a train. Could always be quicker/faster but it does the job.............. for now