My favorite tweak is the "cable lifters"
That my friends is a 7.2kv poletop porcelin insulator. Why would we need a 7,200 volt rated insulator for carpet static? At $50+ each I'd bet the farm that using a few blocks of wood, some plastic cups, ceramic coffe mugs, etc would work just as well.
A lot of people swear by cable lifters. Most of the DIY guys use chopsticks or other cheap thing to fashion a riser. Those porcelin lifters can be had on agon for a lot less than $50 each. I was looking at those thinking I would get some if I got any audible result from a cheap diy attempt. Initially I tried upside down ceremic mugs as lifters. I did get an audible effect - that was my girlfriend saying "wtf are those things doing? You aren't leaving those there are you?". I have no doubt that in a blind A/B comparison, you'd hear the same thing in your system. Other than that, I didn't percieve any benefit in the sound from my system using the ceremic cups. I also tried paper tubes (toilet paper rolls) and that did nothing. But many people report good results, so I don't know what to think.
I did hear a benefit when I installed cones/spikes under my speakers.
I heard a negative influence using BDR cones under my amp and under my CDP but they were just set under there, not afixed. So maybe not a fair test.
I also have heard benefit of routing my cables ot keep them as far from each other/crossing and 90 degrees.
I heard a small benefit from putting a 10lb iron plate on top of my CDP. (standard black iron plate used on dumbbells) I heard a much more significant improvement in sound by leaving the CDP powered on all the time.
I think I heard an improvement with the Herbies tube dampeners - but the result of those depends on how microphic the tubes are to start with.
Tried the caig pro-gold to treat connectors. I reseated the connectors a few times to get a mechanical wipe and tried that before trying the pro-gold, just to try and isolate the effects of progold from the effects of mechanical wiping. Heard a mild improvement in clarity. Silclear is supposed to be even better.
I'm sure a combination of the effective tweeks can amount to a nice improvement in any system. But for my money, upgraded main components and speaker placement have yielded the most audible sonic improvements ahead of room treatments (panels and room lenses) with tweaks being far behind.