Alright, after doing some research the solution seems to require the following:
Sedan FRONT control arms
Sedan FRONT swaybar
Sedan FRONT endlinks
Sedan REAR lateral enlinks
Those will allow me to put whatever 05+ STi suspension I want on my 05 hubs, as far as I can understand now. Will the front control arms bolt up to my WRX as is or is there some kind of mod I need in order to make that happen? It seems that if I can get those on, the rest will work...