Why do some amplifiers throw a bigger soundstage than others?

If soundstage cannot be measured, does it exist?  

If love or music as some specific arrangement of sounds cannot be measured as such do they exist ?

A children will say yes...

Soundstage is an acoustic perceived parameters pertaining to many contributing factors with are related to the electrical, mechanical and acoustical characteristics of the gear /room but also to the inner ears frequency response and to the HTRF of each one of us and also to the recording acoustic trade-off choices of each specfic album...

Soundstage cannot be measured in a simple linear way but it result from a perfectly contrallable set of parameters.. I put it under my own control in my room and sculpt it in a way and the form i wanted too ...

Most things exist in spite of being non measurable in a simple way or even in a complex way ... Galileo eliminated what is not simply measurable, as taste ,colors,sounds,odors and feelings and called them secondary qualities. not measurable as the primary qualities : size,position and location , form and motion to start physics...

But physics as it is now is a drop in the bucket of knowledge ... 😁

We need a new physics by the way...

This dude in India work to create a new physics among others..

If soundstage cannot be measured, does it exist?

Personal subjective theory. As I improved my system with lower capacitance cables and interconnects, purchased a WiFi streamer with a better DAC and lowered the line level from the DAC to my previously serviced older Crown PS 200, the sound stage widened noticeably…I think because the rest of the system had increased frequency response and decreased distortion. The difference had more to do with signal in and cable affect on speaker level signal out than the amp itself, maybe.

It doesn't happen. It's a placebo. The only reason you'd hear a difference is if one amp is underpowered and the other has more power to drive the speaker, assuming the speaker can handle it.

Should spatial perception x what you describe differ for, say, bass in outdoor setups (I am sorry - I realize this is slightly tangential from the OP query)?

@benanders Outdoors we can sort out where bass notes come from. But in most rooms indoors we cannot since it takes a few iterations of the bass note to pass our ears before we can know what bass note it is. By that time (in most rooms) the bass has bounced off of several walls and so is 100% reverberant.