which excels at Rock and Roll

I think it’s personal taste and how you like your Rock. One of the best live shows I ever heard was Supertramp in a theater with ATC speakers. It was smooth powerful and crystal clear. On the other end of the spectrum for me was Lynard Skynard who recorded all of their music in a loud room with a fair amount of reflection. I realize I’m giving a live Vs recorded example, but for me it’s what I’m in the mood for. Chris Issac doing “ Only the Lonely “ has forward clear vocals and a black background. At the risk of getting burned at the stake , I recently bought some Tekton DI’s because I wanted to play classic rock at 100 db. I’ll probably get tired of them in time and get something entirely different. I have JBL , Klipsch and Zu in my spare closet. I rotate speakers and tube Vs SS amps. I’m considering class D amps for next summer as my 180 wpc tube monos generate a lot of heat. We’re never satisfied , Mike B. 

I have to disagree that components equally reproduce music of all genre. That is the ideal, but in reality it is not true. I used to love electronic music, and I went out auditioning with several electronic music CDs. Like Enigma. I optimized them with speakers and electronics that added to the ethereal nature of the sound. This had drawn me to planar speakers and supporting electronics. But, all the other music sounded worse and worse. This just one of my attempts to use a small selection 

I later optimized on details... and ended up with an incredible system that showed every flaw and made clear the mastering and ambience of the recording... and took the life and soul out of the music... But I could hear every detail in the music. 

Ultimately I spent years tuning my ears to real live acoustic music and used that as a reference, and finally all genre got better at the same time and the soul of music and emotional connection came back. 

Anyway it may not be on purpose, but lots of different equipment makes certain genre sound better. B&W and MacIntosh, with their real heavy bass and midrange let's Ozzy's "OH GOD NO!" followed by an incredible rush of bass and midrange overwhelming. But put on a string quartet and you are missing the details. 

I think Class D never works with Mumblecore.

@robshaw  Your opening comment "Room is 14X14' No treatments, but, room currently sounds great" has me perplexed.  Everything I've read on listening rooms says the worst is a square box.  I can only guess how much better your system would sound with acoustic treatment, regardless of the speakers you go with?  Just a thought.  Cheers, 

For rock, pop, percussive, symphonic, and electronic music you need good speakers with good dynamics.  The rest will sound as it should as well.   So speakers like that can handle all music well and are not genre specific.  Planars and Electrostats tend to have limited dynamics so not as good for the types mentioned above and therefore are more genre specific.  But it’s hard to make the case a speaker is top notch when it can’t handle all kinds of music well. IMHO based on years of experience, that is. 
 

Size matters as well depending on room size and ability to go to lifelike SPL levels, though not all may necessarily need that.