Take a look on nasioc.com. It is the biggest subaru website in the world (and like top 5 biggest web forums in the world). So there are generally quite a few cars for sale there. If you have any questions about the WRX feel free to pm me.
I picked up an '03 wagon for my dd. My STi is at the end of a major overhaul and should be around 550awhp on pump. So the little subies can handle quite a bit of power.
Nick