With a proper tune and good maintenance, I hope 350awhp is reliable...If not, Subaru needs to do a little better job putting engines together. I know it's comparing apples to oranges, but its not uncommon to see stock 1.8L B series Hondas pushing 400whp on stock blocks...if they can do it with 2/3 the displacement and cast 10:1 or 11:1 pistons, i hope an STi can handle it.
Next winter my STi will be getting a few new toys and with ~100k on the clock, i'm looking for 380-400awhp on corn. I guess we shall see how it likes it