I've had both the refrence and the kappa series. I found that they all are a little abrasive. With the Kappa's I couldn't listen to evenescence it was almost painful at louder volumes. I ended up switching to the JL Audio C3's which were way smoother in that car, however the JL's sound like crap in my current car. I am now redesigning my car for the audison AV K6's wich may be the best speaker I've ever heard. ( to my prefrence )