Using familiar recordings is the key. You might be taken with the latest Taylor Swift Ode To A Tight End, but if you haven’t heard the piece on a variety of systems it may not be the best piece to asses new equipment.
I listen to Classical and I have 3 pieces that I use:
The first is a recording of Sibelius Fourth Symphony , released originally on EMI (now Warner), with the Berlin PO and Herbert von Karajan. I use the slow movement (writen when the composer was being treated for throat cancer), which has deep string choirs, an oboes that goes fromm very soft to very load in the space of 16 bars and back again, and ominous, menacing brass. I have had more than one stereo salesman inquire "What is that music?" in admiration.
The other is a recording of Didos Lament ("When I am Laid In The Earth") featuring Emma Kirkby. It starts off very quiet, and Kirkby doesn’t have the biggest voice compared to others that have recorded it (Jessye Norman, etc) but the volume and intensity ramp up and Kirkby has laser like intonation; I have found that systems that get this right will do well by vocal recordings
The third piece I use is actaully a poor recording, because it is important to hear how a system treats poor recordings. The Pianist Wilhelm Kempff recorded Beethoven Piano Sonatas several times, but the one I use is from the sterreo set made on DG in the sixties. The treble on the digital transfer is awful-make your ears bleed on a system that accentuates brightness. So while it is far from a favored recording, it is useful for auditioning equipment