It is no myth, and you don’t need to spend a ton of money.
But you do need to get things right.
The speaker spacing, both to each other as well as the back and side walls, is very important. You also want "time alignment" between the drivers. And you want symmetry in the room. Soundstage/imaging/depth are all dependant on constructive as well as destructive interference and phasing and for these to occur properly, both speakers essentially need to be the same and "see" similar environments so they are the same in the seating area.
And..., if you want to feel "encompassed," you’ve got to bring the volume up to realistic listening levels!
I know it sounds cliche, but I’ve spent years putting together and perfecting a pair of speakers that image like no others I’ve heard. And I have JBL L200/300, JBL L112s, Altec, Big Red Supers (triamped), and Chartwell LS3/5As, and have heard Magico and Focal at demos, as well as lots of other varieties at listening parties.
If you get down to the Orange County, CA area, you are welcome to come by and hear what it is all about. Meanwhile, I leave you with this YouTube video. This is just the two inner speakers playing with no sub attached, no eq, and no room correction, either physical or electronic. The room is large (27’ x 16.5’ x 7-1/2->15’ ceiling, and open to the entrance hall and dining room.
This is an SACD played on an Oppo95 ($300 used) through a Yamaha RX-Z9 RECEIVER ($4,050 new at 10% off in 2002) in "Pure Direct" mode. The speakers use a JBL 18" 2241H, JBL 2251J, and ESS Great Heil that I’ve modified ($1,500 total investment with used drivers but new crossover components from ebay).
This shows the spectrum in the seating area without the 18" connected to alleviate the "noise" associated with floor and room bounce. I know it look a bit "bright" but that is a personal preference and I think it makes music more lively and brings out the microdetail. As shown, the crossovers are all the way up and there is even a "flat switch" that removes the upward tilt, engaged for overly bright or noisy cuts.
All caps are Audyn Q4s, all resistors are Dale 1%, all inductors are heavy-gauge air core.
So what do they sound like? Well if you believe in YouTube (many don’t) put on some really good headphones and take a listen. And while you’ll hear a nice smooth response, and lots of detail, you loose the imaging, but are welcome to come by for a demo any time. This was recorded on a Nikon D750 DSLR.
https://youtu.be/oLgQCHmXSUU