Doesn't matter if it's an STI block or not
A stock unopened STI or wrx/liberty can handle upto 220-230kw@wheels before u worry bout a piston popping. That's the 2.5s.
As for the 2.0litre depending on what the pistons are in it, if cast like the 01-02 wrx maybe 210-220. If forged like 03-05 STI can hande 230-250kw@wheels.