What music do you use to assess your system?

Oh boy, and we've officially digressed, 4 posts into the thread.
WARNING: do not watch that video unless you have 4 minutes to burn. You will never get that time back, and you will not be able to stop the video once you've started watching it. Thanks for the laugh!

Geez, I watched the video too, I'm speechless. Words fail me.

Now, back to the original OP's question. Some of my tracks I use to maintain a baseline of familiarity when auditioning new equipment might be Rautavaara's "Cantus Articus Opus 61" for its extraordinary sense of atmosphere and orchestral treble nuances, Bela Flecks old standby "Flight of the Cosmic Hippo," Keith Richards "Rockawhile" for its sense of timing, groove, and kick bass drum, Bill Frisell's "Blues for Los Angeles," again for groove, swing, and propulsive bass guitar, and Hovhaness' programatic "Mount St. Helen's symphony 50" for the entire palette of orchestral instrumentation, dynamics, and tone color.

Dave Grusin's Two For The Road. Not only is it enjoyable to listen to, but it contains exposed portions which really make it easier to judge a system; female vocals, piano, brass, percussion, and bass.

What the fox you sayin'?

I think that the best example that I have found is Christina Aguilera's Christmas album. Her vocals will quickly expose flaws in a multi driver/X-overed speaker design versus a single driver or coherent design such as the Quad ESL speaker. This is an excellent album in all respects including bass! Hope this helps you.