Soundstage depth is real. I hear it on almost every recording. Except the lousy ones. For the record. I use Watson Labs Model 10 speakers. They are dipoles with subs. My room is carpeted and treated to minimize echo. I find more depth with dipoles than any other speaker. I believe. But cannot prove. That depth is also a function of the distortion profile. Mostly even order harmonic distortion proveds more depth. I came to this conclusion adjusting the distortion profile on my 80 wpc first watt v3 amps. This could explain why some say tube amps give more depth...