Best air filter panel for...
 

A standard 05 WRX wagon with 'PPP'. Also what benefits can I expect from changing from a standard panel? BHP, torque, sound?

get a k&n or green panel filer. slitly better torge and a sukin nosie above 3krpm

The OEM part, unless you intend to increase power. The other make more noise and can lower BHP. There's plenty of posts if you try the search facility. Regards. Bob

Green here too.

I like the sound of the suckin'! :)

OEM is good and the Green filters are as good. KN is also worth it as it's reusable and only needs a 'light' oil at service intervals. KN do guarantee the filter for 1,000,000 miles so it should last! I don't think there is any power gains proven by any of them just a slight increase in induction noise.

Green filters are the same type as the K&N,in that they too need cleaning and light oiling but are also guaranteed for 100k miles.