I don't think you can Tino.
I looked at 3 2002 STi's for Dave master D, all over 20k and none I would call decent. They may look and sound decent on carsales but often the actual car has hidden 'bonus' extras.

$15k isn't too much for a really good GC8 I reckon.

I know Darren's old car, happy to inspect it if you like.