What makes the biggest difference in sound quality?

It would be easier if the question was a poll for say fuses. (Like, don’t like, don’t care)
Then a different thread for ICs… etc.

Or a poll with the 4 things in some matrix which is either 4^3, or K-choose-N or maybe is 24 ranked options? (I would need to take off the shoes to do the maths)

But I like multiple choice questions as they are easier to sort and analyse, than open ended essay questions.

System matching is the most important aspect of great sound. Having a system of equals works in harmony with everything else. Pairing a expensive pr of speakers with less than electronics results in frustrations and miss guided assumptions that some how the speakers are flawed. With this example your assuming the speakers are the fault because they sound less than perfect; when in fact their level of resolution exceeds what your other components have to offer. Balanced system is the key. 

I think quality speakers make the biggest difference. I know folks will go on and on about amplification, source, etc., but speakers have to be quality or the sound falls apart. 

I am interested in knowing more about how to check refrigerator compressor symptoms. How can I resolve this issue immediately? 

System matching is the most important aspect of great sound. Having a system of equals works in harmony with everything else. Pairing a expensive pr of speakers with less than electronics results in frustrations and miss guided assumptions that some how the speakers are flawed. With this example your assuming the speakers are the fault because they sound less than perfect; when in fact their level of resolution exceeds what your other components have to offer. Balanced system is the key. 

Good god, not yet another synergy and balance echo.