You can make a pretty strong argument that there’s nothing approaching a “soundstage” in most live performances, even in small venues. To me the soundstage engineered into recordings for our systems is primarily to give us aural cues in the absence of the visual cues we get with live performances. It’s artificial, but pretty cool. That’s why some very sophisticated audiophiles - not all of course!! - are not fanatical about soundstage. Art Dudley, one of my alltime favorites, may he rest in peace, was in that camp, I believe. It also may be why some prefer mono recordings, and are not huge fans of Rudy Van Gelder (whom I love).
The best reference is live music
For those of you who love classical music and care about imaging in your audio system, I recommend that you check out a San Francisco area group called Voices of Music.
They video record all of their performances and have most all of it on YouTube and free to access. They are extremely well engineered recordings and more than worthy for the very finest audio systems. What makes these recordings especially *useful*, as well as enjoyable, is that being video, you can see where all of the musicians are. The best reference in audio is live performance. Does your system do an honest job of recreating the live performance? Does your system give an image that at all matches what you see on the video?
Beyond this issue, Voices of Music is worthy to experience because they are very different from the large symphonic performances that most classical listeners hear. Instead of the SF Symphony with 100 musicians, Voices of Music will typically have about 8 to 12 players. There are some larger ensembles and some smaller.
They are an "early music" ensemble. Just as rock 'n roll evolved from the early 1950's to what we have today, what we call classical music evolved as well. The instruments evolved too. A 19th century violin (what the musicians call "modern") has a neck pulled back, has steel strings and is engineered to be louder than an 18th or 17th century violin, which has a straighter neck and gut strings. They are in fact, different instruments.
An 18th century instrument will articulate better. The bow is lighter and faster than a 19th century bow. Trumpets of that period had no valves. Neither did French horns. Flutes were typically wooden and had open holes. That period also had instruments completely absent from "modern" orchestras. If you haven't listened to a 1st rate early music ensemble, you're in for a totally new experience.