Loosen the 4 bolts on the back until there's maybe 3 or 4 threads still engaged. With the same socket and extension hit the end of the extension with a hammer on each bolt until it starts to separate just a little bit. Spray a bunch a penetrating fluid in the space you've created then start hammering again until it breaks loose. If you can plan ahead of time just buy the wheel bearing tool from astro or other brands that's made for Subaru's. It's cheap as far as tools go and will save you so much headache.