The design of both intakes you mentioned are arguably the most ideal setup for the car, and the gains (at least for the Stillen G3...havn't seen much out of the Injen yet) back that up.
You can spend two or three times as much for perhaps kit from one of the Japanese tuners, but I highly doubt they would be as effective as the Stillen. It would be nice to see some more people going with the ARC product, but I'm just saying that because it's pretty.
