Not worth it. I had them on my old CRX so I can't really say how they perform on the Impreza but I was unimpressed with them. Lots of dust and no noticable increase in stopping power. Get some porterfields or Hawk pads. Granted, I don't know what you'll be using them for but Porterfield and Hawk both make great pads for street and/or track use.
I used them on an Integra before. Like the first response I wasn't impressed with them at all. I was pretty happy with a set of EBC Green pads but that was mostly because they didn't require heating up to work even when it was cold out.