How you know your system is improving?

Fellow Audio Junkies - 

Over the last few years, I've invested in my first high end system. It's been a far costlier affair than I'd initially conceived. I started off simply wanting to listen to music in my home. At this stage of my life, I was fortunate to have some resources to invest which led me down the path of reading forums and reviews, while also having the opportunity to visit a few audio stores to demo equipment.

And down the rabbit hole I went... Once I realized all the nuances of equipment and their impact on the listening experience, I became fascinated with creating the most satisfying musical experience in my house. I ended up purchasing several amps, three sets of speakers, NOS power tubes, and a myriad combination of power cords.

With each investment, I would often remark to myself "yes - I hear an improvement..." But sometimes a doubt would cross my mind. Is this some sort of confirmation bias I've got going? Am I just throwing money away? Do I need to see a shrink? 

Admittedly, I was largely convinced things were improving, but a small part of my brain recognized I might be have been chasing windmills... 

Which brings me to this question: "How do you know your system is improving after you've made a system change or hopeful upgrade?" 

For me, a moment came last night when I put on a piece of music - Beth Orton - and played a track that a year ago sounded muddy or poorly recorded. There have been several system changes since I last played that Beth Orton track. As I began streaming over Quboz, I could hear details in the music which had been previously fuzzy and hidden. The tone of her voice was more real. Guitar strings came out of the fog... 

I guess the concept I often read about here, "using a test track" had become my new litmus test on whether my system was improving. It was inadvertent, but I think I'll default to this approach more consistently moving forward, going back to a few tracks that have proven to be challenging with the current system and giving them a go when a new component gets added. 

Yes, I know... nothing radical here. But would welcome how many of you benchmark improvements in your own systems!