I got these installed today from my local audio store. I use to have Infinity 6"x8" in there and I can honestly tell you that these speakers are that much better. They are the clearest speakers I've ever heard (I'm no speaker Guru so take it as you will). I played a store bought CD so that I could get the best sound quality out of them, and they totally shocked me. I recommend these speakers 100%.
Highs: Amazing midbass, and highs. Very clear sounding speakers.
Lows: Really big speakers/crossover so you better have a deep door to put them in.
Which set did they replace? Infinity Reference, Kappas, or Kappa Perfects? How do they compare to Polk, Boston, CDT, or Clif Designs? Did you know that Infinity and JBL are made by the same people (Harman)? Did you know that the 608s and Kappa Perfect 6.1 are almost identical?