But I do agree with JLM, most cheap tweaks that I have tried have not worked for me.
I have found many free tips in the site of the Physicist Peter Belt, many of them were musically revelating and useful in my system, I tried most of them and all have a audible effect in my system of that time, some of them had a very subtle effect or a effect that I was unable to say was better, neutral or worse to the music, but all made something sound different to my ears.
Also based on the Peter Belt tweaks I invented some new tweaks I use til today, I cant think in hi quality audiophile audio without Peter Belt.
Why JLM did say that is beyond my little knowledge, since there is tweaks in all the web and hi-fi books.