@newton_john great discussion you've started. Maybe I'll have a nugget worth sharing.
One thing I haven't heard discussed is the type of music people like. I think complex orchestral works are maybe the toughest for a system to handle due to all the dynamics and soundstage required to fully reproduce a symphonic piece. So those that listen mainly to classical, I think probably are more apt to upgrading their systems compared to someone that likes jazz or bubble gum pop music. The genre does matter. If your systems goal is to reproduce the nuances of a live orchestra, it's going to be a life long journey.
The other thing I haven't heard discussed is that an upgrade can sometimes reveal flaws in other components. So what wound up being a single component upgrade becomes a money pit as you realize how you need new cabling etc to refine the sound. This happened when I demod a T+A Dac200 and realized uh oh, the clarity I'm hearing now reveals that other components need some taming (speaker cables, power cables possibly) and decided no thank you on another rabbit hole. This is a super important consideration in my opinion. Sometimes one component change, especially speakers, amp or DAC can throw you down a whole new price tier.
Another thing is that sometimes "better" is not better in all context as maybe some recordings sound more harsh or etched on a better system. A lesser system can provide some "cushion" to some of the harshness we can hear. Probably one of the reasons that people choose vinyl or tube amps (not to say there aren't harsh sounding vinyl rigs or tube amps but generally they are "softer") . This isn't to say not to upgrade. Just remember it may throw you down the rabbit hole of synergy that can mess up your bank account and take you away from listening to the music.
If you really love your system, probably best to keep the speakers and amp you have and try to match components outside of that to tweak it. Food for thought

