Long time ago, I put a Perrin lightweight pulley set on my 4EAT RS. The results were awesome, as the car pulled just a little bit quicker through the RPMs. A great way to speed things up on an automatic, since you can't just swap in a lightweight flywheel.
As for breaking loose the OEM pulley bolt. Have a couple of friends handy (at least one), a 1/2" drive breaker bar, and a cheater bar. You can put the transmission in a drive gear and turn the engine off, you just won't be able to remove the key. Have someone stand on the brakes while doing this, to aid in keeping the car/tires from rolling. Then, start pushing/pulling away on the OEM bolt. The longer the bar, the more leverage you can get on the bolt, but try and use a tactic similar to an impact gun, not just brute strength.
The impact gun works because it imparts many sharp, fast, forces on the bolt/nut, which help to break them loose and rotate. So, apply pressure to the bolt until things stop turning, and then "bounce" the breaker/cheater bar to do something similar. Or, hit the tensioned bar with a 4lb deadblow mallet.
You'll have to remove the radiator/fans to get enough room for the impact gun. If you are willing to do so, or need to flush the coolant, the impact gun will make things MUCH easier.
Kartboy makes a good pulley as well. I installed one on the forester and couldn't be happier with it.
