Ouch sorry to hear that. In my case it was internal engine failure..ie: rod bearing but it was knocking like a woodpecker , and I couldn't go more than 20-30mph towards the end of the damage.
Tranny problems suck ass too cause it ain't cheap to fix or replace.

Hope it all works out for you though!

P.S. if it is tranny problems and you end up getting another car..go with a Legacy or an STi..I say that since all of us WRX guys always have tranny problems in the back of our minds...since it is one of the weaker parts of the car on a WRX...however...not too sure about the newer WRX's.