A lot of people ask which kind of speakers fit in the rear. I found a super cheap and good sounding replacement for the crappy rear speakers that my impreza came with originaly. It turns out that the Acura Integra speakers that i had laying around are a perfect fit. The three holes line up right and the original mounting screws can be used. Also if you dismantle the connectors properly you can use the factory connectors which negates the use of electical tape or solder. The Integra speakers are rated at only 15 watts, but the magnet is twice the size as the Subaru's 30 watt speaker's. The sound is much improved. I can actually feel the sound vibrations when the engine isn't running.

The cool part is you can get these speakers for next to nothing at team-integra.net because they all upgrade theirs.