Recommend a recording that shows of soundstage

Believe it or not...Vogue by Madonna. I believe it is on the Immaculate Collection album. This is recorder in Q-Sound and there are parts when she goes into vocals where her voice comes from all corners of the room if the system is capable.

"Before The Deluge" by Jackson Browne is the one tune I always use for this.

Nils Peter Molvaer on ECM CD, Germany;
The Orb -- experimental electronic music project on 2xlp
Ashkenazy plays Rachmaninoff Piano Concerto 3 on Super Analogue vinyl.
Actually none mentioned Dark Side of the Moon yet...

Cowboy Junkies - Trinity Sessions

Mercy Street, especially the opening bars, from Peter Gabriel's "So" album.
A lot of the tracks on Steely Dan's "Two Against Nature" and especially the track called "True Companion" from the compilation "Steely Dan Gold."
"Morning Bird" from Sade's "Soldier Of Love" album. The entire room should be immersed in the piano.
Pretty much every track on Dyan's "Oh Mercy."
"Dark Side Of The Moon," of course.
I'll think of others...