So how do you tell when you listen to a system (or yours) whether the issue is with the system or the system revealing something in the recording that your equipment doesn't?
I would say that no matter how far up the chain your equipment is, the (system) can always be improved. That being said,you reach a point that a good system get's closer to the actual source(master tape or digital master) and incremental steps get smaller.
Depends how you listen and what you focus on. Some will not hear any difference,but for a critical listener making a change,provided knowing if a change should yield a improvement,the listener will notice. I listen for clarity,weight,fulllness,dynamics,PRAT,ambient retrieval and soundstage width,depth,placement,ect. How close are you to the master tape? Now I listen to a lot of tape and make changes to the tape electronics. That is where I can really tell the difference between a transformer,cap and resistor. YMMV
Myles...your ?? was not directed toward me,but happy to answer