This is a great thread. When I was auditioning speakers recently, I just brought with me a handful of CDs of different musical genres (classical (something with an orchestra), jazz, rock, world, and something with great vocals). This really helped me think about how the speakers sounded playing different kinds of music. But the nuforce concept CD was probably the most helpful of all the types of music I brought in auditioning speakers.
By the way, I wasn't too worried about how familiar I was with the music I brought to audition speakers with. I had listened to all the CDs before but they weren't necessarily ones I listened to regularly. I'm curious how others do it because I've heard conflicting ideas on this. Some say only use music you know very well (since that gives you a solid reference) and others say you should use music you are less familiar with (presumably because it forces you to listen to something for (almost) the first time).