They've got to be have heard them with all kinds of music including pop, rap, electronic as well as the usual audiophile stuff.
Interesting, quite a few votes for ESL speakers. I've never really heard any ESL but I've read they are pretty light on bass? Wouldn't that make them pretty useless for rap, electronic dance music etc?
Hard to pick between the two, but just glad to have found a space for both of them.
I'll ignore the OP's requirements as I use speakers for music, not rap.
For me the best I've ever heard would probably be Quad ELS57's and Linkwitz LX521.