The ’what to do after you already have a good system’ mentioned by axo0oxa is a good point. And something I could add to.
Once I have a ’decent’ system, (2010) I left it for a number of years. Mainly I finally bought some high end interconnects. Then I started last year on the system again, starting with te best speakers I would ever buy. Going from 3.6 Magnepans to 20.7 Magnepan.
I wondered what to get next, but ended up buying a high end SACD player to use mainly as a DAC. (The usual thing to get, a new amplifier, my trusted dealer said I did not need one, So I accepted his advice..) I COULD have gone for a Rega P10 turntable. But my previous DAC was a used $250 device... And I thought I also own already a Kuzma Stabi/Stogi S turntable which is pretty good already
Then I suddenly got back to some basics. Power cords, a few, that instilled the ideal to finally buy some real better AC duplex. and actually that was because they were on sale, getting something that is considered on of the best possible, at half price,, I jumped on it! Even though I did not start out to do it.) Discovering how much a difference a few made, I went crazy and replaced the entire system wide duplex, including replacing the AC duplex in the two power conditioners.This also was a ’get the best I can’, since I will never re-visit buying different ones. I went back to a basic underlying thing. (like when I bought cables, so those would last through other changes.)
So I kind of would say there are TWO areas of a SYSTEM.. the main part of components, and the underlying structure, like cables, AC, cords, conditioning, even racks.
At this point I am resting.. Actually just adjusting (still) the little bits, like the resistors in the midrange of my speakers. After spending months critically listening and adjusting... I am tired of it, and just want to listen to music...
But in the future.. I can see revisiting the turntable upgrade, and by another year will need at minimum new cartridges for my two TTs.
So my upgrading went in two cycles, the components, and the support system of cables etc. Curious the components, I cannot really say I am finished, the support some parts I did go as far as one can go.