For cats, I asked my local custom exhaust shop(not midas or chain place). They told my $100 for a ceremic cat welded in plus whatever piping they use to fit it all together.
also, i thought with track pipe the wrx/sti cat/axle back turn the sound raspy.
Us 06-07 2.5i's cant use stock cat pipe. its integrated into the headers. Gee-otto is working on a group buy for us to get a set of UEL's with factory positioned cats for us. I'd love to go in on it, but its kinda out of my price range atm.