A bit further away, a company in New Zealand called SUB4 modifies EA81s (and probably other subaru engines) for Aero use. Their modified EA81 features a high compression cylinder head with twin ports for both intake and exhaust, twin spark per cylinder and a bunch of other goodies. I'm not sure on the prices, but when the Kiwi dollar weakens (which it unfortunately inevitabley will) it could possibly be an option for you US guys.
http://www.autoflight.co.nz/dominator/features.php