I remember my main criteria when I was shopping for speakers; they had to be able to play "Bron-Y-Aur Stomp" off Led Zeppelin III without distorting, LOL. John Bonham bashes his kick-drum harder than on any other recording, and John Paul Jones bass was starting to breaking up as well.
I took the CD to the store and the KLF-20s did the job better than anything else.
The good news is they sound wonderful on other types of music, too.