For me, Steely Dan's and their frontman, Donald Fagen's albums are choice picks for auditioning. They were truly a band that paid close attention to the recording and mastering of their work. Both the "Gaucho" [Hybrid SACD] and "The Nightfly" [CD] have excellent sound and the former is possibly one of the best SACDs on the market. They also typify that 70's-80's sound that I enjoy (smooth, not the annoying disco that came before or the kitschy pop that followed).
The remastered Miles Davis "Kind Of Blue" CD is an excellent reference for jazz. As is the John Coltrane "A Love Supreme" SACD.
For good old rock I use The Kinks' The Ultimate Collection 2-CD set. Very deep and full bass that really gives the woofers a workout and very good mastering in all. Possibly the most "analog-sounding" recording I've encountered.
For vocals, I use either Nina Simone, Ella Fitzgerald or Eva Cassidy albums. In general most Verve and Telarc label CDs make for good test CDs.
The remastered fifth Peter Gabriel album "So" is a good all-round CD with a diverse lot of instruments. The haunting opening strains of "Mercy Street" or the percussion on "This is the Picture" is rather telling.