Speakers and depth...

Anything with a "BBC Dip" and a warmer less defined bass will tend to give you a deeper soundstage. Upper midrange rolls off with distance and bass sounds less tight or crisp as you get further from the stage.

Rogers is a classic example but many follow the same design principles. Look for a speaker plot with a dip in the upper midrange and particularly a roll-off in the off axis response in the upper midrange (off axis response clues you in as to where instruments are - if it is in your room and close to you then the off axis response is very strong as you will well know if you play an instrument - if the sound is far away then the off axis will be even weaker or more attenuated - these are all clues that the source is far away giving the impression of a deeper soundstage)

The room is very important for this as is placement. Got any room treatment?

ET

I had a pair of JMLab Electra 926's that put out a soundstage exceeding the boundaries of the room that they were in ! They are the only speaker , that I have heard , that created a soundstage behind me as well !

It is partially dependent on the source and software too .