I jus been through this after one of my pistons melted, not sure bout an sti conversion, but was i was lookin at 96 sti front cuts for a bit over 4g, dunno how much labour would be, 2.5L, if you are interested, was bout the same from what I remember.
If you were goin to sell it, the second hand motor is prolly the cheapest way. I rebuilt mine, purely coz I wanted to keep my car and I kno now i'll never have engine problems.

If your thinkin of sellin why not jus put a std wrx motor in it?