A few tweaks I have been doing for years. As many here might know, I damp horns, woofer frames, cabinets, equipment chassis, everything. Another tweak that for me was always significant with improved sq was to remove the power cord from a power amplifier (non IEC inlet) and install (hotwire) a heavier duty power cord/plug to the design. A couple that come to mind are Adcom, Soundcraftsmen, Hafler, Phase Linear, SAE, and so many more. It turns out, the puny power cords on these amps are a bottleneck to the capability of the amp, as some of you might imagine. I also attempt to decouple the power transformers from the chassis, which on some designs makes a significant improvement in sq. These products are always "out of warranty", and never had an issue. My best, MrD.
My Favorite Tweaks, What is yours?
My favorite tweak is Puron lowering noise floor of my system. Holostage they open my system more, bigger soundstage , improves layering as well ,and made my system more effortless to listen.