why do expensive amplifiers produce a better soundstage

I think one of the most important factors is the quality of the recording because no matter how good your system is the recording is what it is.

Further, compression of the recording and detail available to transmit through the room via pressure amplitudes is really important to overall soundstage. The density of the pressure amplitudes and it's impact on your inner eardrum is ultimately what it's all about.

It's kind of like porn you know it when you hear it. It's not rocket science

If you had the experience, you'd find that it's not actually the case.

Share it. This is what the forum is all about.  Maybe you could give AI and everyone here a good lessen what actual soundstage should feel like.

@yamaho soundstage is the result of at least : left right matching, phase accuracy, dynamics… just like everything else Audio, the diminishing returns principle applies

i've been using Allnic Audio w upgraded tubes and Shunyata Theta NR for the last five years, nothing so far has touched it.  Simple circuit.  

It is a physiological response to wallet depletion.

In my experience, different DAC's made for better soundstage.  And later, on a particular DAC, upgrading the capacitors in the signal path to films increased the clarity and soundstage / imaging.

I'd say if you changed ower amps and noticed better soundstage, then the input stage of said amplifier was just better.