"Litmus test" songs

I always use these well recorded cuts:
. Diana Krall - A Case of You (Live in Paris)
. Rahsaan Roland Kirk - A Laugh for Rory (Inflated Tear)
. Art Pepper - Move (Art Pepper + 11)
. Terje Rypdal - Chaser (Chaser)
. Steve Hunter - The Idler (The Deacon)
. Otis Taylor - Resurrection Blues (White African)

And these not so well recorded cuts, but expect them to still sound good:
. Rory Block - Last Fair Deal Gone Down (Last Fair Deal)
. Paul Butterfield Blues Band - I Got a Mind to Give Up Living (East-West)

And this poorly recorded one which I only hope might not sound too awful:
. Reverend Horton Heat - Lie Detector (Holy Roller)

Paul Simon - Graceland - Boy in the Bubble, Graceland, Diamonds on the Soles of her Shoes

Steve Miller - Born 2b Blue - God Bless the Child

kd lang - Absolute Torch and Twang - Luck in My Eyes

Talking Heads - Naked - Nothing But Flowers
Talking Heads - Stop Making Sense - Burning Down the House, Life During Wartime

Miles Davis - Kind of Blue - So What (Columbia Mastersound) - only the bass in the beginning

Those will usually show up deficiencies pretty quickly. After those, I go to acoustic music, etc.

Another trick I use in testing out equipment is to try out flawed recordings. e.g. If you have a recording where you know that the guitar has a marginally harsh edge, then a great system doesnt correct this for you, or it will fail elsewhere.

Here are some albums I always take out.

Soundstage: Paul Kelly, "May 1992"
Electric guitar/decay,surge and whomp: Midnight Oil, "Earth and Sun and Moon"
Acoustic: James Taylor, "Fire and Rain"
Live Ambience: Neil Young,"On the Beach" and "Zuma".