But the Raptor kit (which is the only commercial kit available for subaru engines) is a centrifugal S/C so it wont give you much if any more low end power, you would have to use a Roots/Twinscrew/or maybe a Rotrex to see any low end benefit but all of this would require quite a bit of custom fabrication (its been done before though).
Frankly i think a SCed ej22e would be a great little workhorse.