Is soundstage DEPTH a myth?

Depth can happen on a boom box no problem, it has nothing to do with the sound system it has to do with the way the music was recorded. I've done thousands. 2 mics over the conductors head will give lots of depth. Why do audiophiles assume that music is all miked the same? Modern music isn't recorded for depth it is close miked with a multitrack recorder.

The album

Gabi Hartmann - Gabi Hartmann

is recorded with lots of depth in the soundstage.

Hear i.e the piano and woodwinds on track four.

Real depth or created at the mixer board?

Electronic music often have created depth in the soundstage.

Sound "appears" to come from far left and right, well outside the speaker placement width.

It also appears behind the speakers, in front of the speakers, apparent height is also heard, and if you have a nice setup you can actually hear sound that appears to come from behind the listener.

You don't need expensive equipment to hear this.  A definitely not audiophile, fully studio manufactured, recording I use for a lot of demos is Led Zeppelin II, side one.  If you can't hear the swirling up and behind your head on track 1 your speakers/room are not set up properly.

Chesky demonstration disks can show all of this.

No, it is not, but it depends on your music.  Classical music from Telarc, LSO, and a few others exhibit great soundstage width and depth.  Pop and rock not so much.  Key to the portrayal of a deep soundstage is having the speakers well out from the back and side walls. 

@samureyex No sir! When you start getting depth in sound stage you know you’ve got things right with your system. The right component’s, cables, vibration control, power conditioning, and noise floor, all in harmony. Anyone who tells you different is kidding themselves and has not experienced great soundstage. This is almost the holy grail and what we’re trying to achieve. I’m here to tell you it is really something when this happens. In my case with attention to all of the above in many years of tweaks and upgrades, I achieved this with a bluesound node, of all things..When I finally installed a fiber optic in my Ethernet cable feeding the node…boom! It kicked in, and it wasn’t at ear splitting listening levels, rather normal listening volume. It was a really nice experience, and felt rewarding. The only bad thing it made me spend more money by replacing the node with a much better streamer. But now I have a much more satisfying system. This hobby will do that to you if you’re not careful. Keep searching.