Stillen is the loudest i would ever go on purpose, any louder is straight up obnoxious. stillen also has an annoying 2.8k resononce.(sp?)
HKS turbo is VERY quit. Ive reved at people at a light and have them not even notice AND i cut out the presilencers and straight piped em. Gets my vote for good quiet exhaust. Supposedly genie is nice too.