i just finished setting up my new system. i swapped infinity three way speakers for the stock ones few years ago, noted some improvements then . then i added polk audio 5" rear speakers; that added more sound, but not more quality. i finally installed a new pioneer DEH-P80MP headunit along with an infinity basslink. i couldnt get the basslink to work, so can't tell you much about it. the headunit in combination with the infinity three ways gives really nice crisp sounds. i would not say its a huge difference, but certainly noticably cleaner sound.