Are future improvements in Amp/PreAmps slowing to a crawl?

High power all tube Class A amplifier. In case it's not clear translates to a HUGE amplifier.

I could tell you what it sounds like. It sounds like no amplifier is in use.
As far as performance - It's more like a 3D sound projector.
The only thing you hear is the original venue fully "displayed" as an acoustic image. Turning the volume up and down acts as a zoom control that changes the distance or your proximity to the performance.

Aside from that being a non-answer...
Why exactly would a volume knob manipulate the spacial cues in a recording? 

bad tracking with channel to channel variation would harm spatial cues