There’s been a lot of good suggestions so far.
Boy, Amir’s testing of some of the “boutique” audiophile type products has been eye opening.
I think there is a bit of a paradoxical effect of the objective instrument testing being done here. Many (most) of the differences in the measurement are not audible. The paradoxical effect is kind of a boomerang placebo effect. Someone owns box A and it turns out to not rank so well here. All of sudden you start questioning the sound, hearing phantom “deficiencies” that were inaudible up until the time you read the test results.
And they likely remain inaudible!
Differences between competently designed amps are inaudible. Differences in DACs are largely inaudible, except perhaps to the most skilled listeners, listening in very high end dedicated studios.
So if your gear has the features you need, fits your room visually, and is reliable then there is little reason to “upgrade.”
Speakers and listening environment remain the biggest trouble spots.
I’m a big fan of Craigslist. There are a ton of bargains to be had if you’re in a bigger city. The main thing is to insist upon doing a basic listening test before buying to make sure it’s working.
If you don’t mind the fussing, it’s relatively easy to sell things too. So you can get speakers at a much lower cost, try them out, and sell if you don’t like.
But my main suggestion is to learn to trust your ears. The recommendations against doing this are related to a specific problem where placebo effects convince people to spend money on things that sound no better.
But ultimately, if you are concerned with putting together a personal system, the main factor is how it sounds. Are you happy with what you have? If not, what don’t you like? Is your gear hooked up and working correctly? Speaker position and room treatment have a huge impact. Can you experiment with this? ( getting a friend to help makes this less painful).
A lot of problems with speakers can be ameliorated with targeted EQ. Even plain tone controls can make a huge benefit.
If you run a computer as a source, it’s relatively easy to run a full parametric EQ. You can use this to tweak your system by ear.
There is also the world of room measurements and filters to compensate.
The main method is iterative. Listen and evaluate what is not sounding good. Make some steps to go in the direction you want, using critical listening to see whether you have improved the sound.
Working at these techniques will rapidly improve your critical listening abilities. As these skills improve, it will become less confusing when you do want to purchase something new.
I think ASR has proved that the audiophile consumer audio industry is largely comprised of companies marketing overpriced gear, often with worse performance than the more reasonablely priced fare. These companies are operated by delusional individuals, at best. It’s ridiculous that people can work for years in the industry and maintain such irrational understanding of how hearing ang audio works.