i have just brought a 52 plate wrx and i am looking for a airfilter and a backbox for it. can anyone tell me what to go for? but i dont want to much noise but power gain

 

Main power gains will come from removing the cats, just changing backbox and filter IMO won't give you much more power, maybe 10bhp?

With a classic (presume newage much the same) you can get up to 30bhp changing full-system and filter.

A lot of people just change panel filter, myself included, green or STi filters are popular. As for zorst prodrive or scoobysport are not too noisy according to others. I have a ninja - pretty noisy but not OTT

Exhaust clicky for Newage