When does one know it's time to upgrade?

@goose 

Sage advice.

@stuartk

" But what i can't wrap my head around is how anyone has any sense of direction when it comes to pairing equipment"...

There is, as someone mentioned, the approach of sticking to one brand-- finding a "house sound that you like", although I've never done that.”

Yep, you did a great job of characterizing the audio journey. You have to learn what you want, which changes over time. You have to learn what component sounds like what and how to tell in a system. You have to make some mistakes. You have to love the journey as well as the end points you reach. 

I’ve been building and upgrading my system for 50 years. More and more I would reach a plateau where all system components were optimized and balanced and I would just stay there and enjoy the music. Then, I guess I would financially recover and slowly start to realize some change in my tastes or shortcoming in my system. I would then be shooting for a 2x cost upgrade of one component... usually the preamp.. So if my components cost say $1,500 each I would look to go a minimum of double... to get the “wow”. But of course that component was now being held back by all the others... so component by component I would swap until the were complimentary and synergisic. Then I would upgrade interconnects and power. Then enjoy the music for 5 to 10 years... then do it again. My most recent upgrades have by far been the biggest and most profound ever, and most satisfying. But then income usually increases with age.  Since I am retired now I have time to enjoy it also. You can see my system if you click on me.

Equipment pairing is hard. If you get equipment with different weaknesses they can work like filters. The first lacks bass, then passes it along, the second lacks treble, then passes it along, at the end well balanced and lifeless. One of the easiest ways to navigate this as you furiously read reviews from The Absolute Sound and Stereophile, and listen to those components is to listen to famous “house sounds”. All Audio Research, all McIntosh, all Conrad Johnson, all Linn... Naim. When you find the house sound you like ratchet back to the components you can afford. This is infinitely easier and more direct route than mixing this component that won an award with this component that won that award... you can end up with stuff that does not sound that good together. My best friend has a $30K that sounds terrible... I could do better with $5K. He has two bachelors degrees and a masters degree in science... but isn’t good with unstructured problems. He makes good individual choices but can’t figure out how to make them play well together.
It is also easy to make decisions based on the most obvious attributes... treble, bass, balance, micro details and miss the big picture. I will note a components obvious characteristic... but then try and forget about it and just listen, over a couple weeks you get drawn to or not to a sound... not concentrating on it allows your subconscious to get its gestalt. I could write many pages on this topic.

Each cycle was also a learning experience in how to choose components and my tastes. I used to have three test disks I would carry around... I optimized the system around those disks... one was electronic. I didn’t realize until later that I was suboptizing all the other music types. It wasn’t until I got season tickets to the symphony 7th row center that I subconsciously started optimizing for neutral... towards making unamplified acoustical music sound right. That basically improved nearly all others. This was ten years ago, and it had the most profound influence on my system choices. If you only listen to Rock... then it is ok to work to make that sound good. But if you want to optimized all music you need an empirical ruler and large acoustical orchestras are really the only way. Everything else is amplified or not large enough scale to test the ends of the volume and complexity.