Av got a pipercross viper induction kit on mine but I got told they need to be set up on a rolling road to run right. alot of the C20XE run like a pile of horse poo with filters on your normally better going for a panel filter
Id go with Green as well. Affordable, high quality and last a long time. K&N's turn pink after a while, even after re-oilling them. Apexi are quite good, I hear alot of rumbles from the states about their filters but to be honest, I dont think there is going to be a huge performance or quality difference in them to warrant the increased cost over a green kit.