why do expensive amplifiers produce a better soundstage

.,,,The Room‼️and speaker placement…. 

here is the answer to your question 

it comes down to parts quality an expensive amplifier uses higher quality better tolerance parts if you use cheap resistors they may not be of the same level they are reported to be same with capacitors enough variation in the circuit leads to loss of signal 

What is expensive?

$2k

$5K

$10K

$25K +++++++++++++++++++++++++++++++++

Those who are buying upper tier equipment also understand room acoustics to a degree. 

I agree that transducers have a greater impact than amplifiers-which have one job, to amplify the signal passed to it, but, of course, a quality designed and built component will allow the rest of the system to perform at its best. Price is not an exact indicator of quality, but unfortunately the old saying that you get what you pay for is generally, maybe not universally true in audio just like anything else.

With that said, the room has a great effect on soundstage and the spatial cues engineered into the recording dictate what is possible.

Correct me if I’m wrong but @yamaho asked about amplifiers and how a more expensive design might improve soundstage. It’s nice to hear other’s opinions on differences among amplifiers and we probably should just stick to the topic; not room acoustics, speakers, etc everything else besides what the OP specifically would like to know more about. There are countless threads about the benefits of properly setup rooms and speakers. @yamaho if you are genuinely interested in amplifier design check out Douglas Self. He has a solid grasp on the fundamentals.

Peace to all