over 2020-2021 been experimenting with the DIY tweak called 'battery ground tweak' (attributed to 'uncle stu' over at audio asylum), adding it to nearly every thing - computer, dac, pre, power, speakers
transforms the system, totally.
modding the super-cheap 6p1/6aq5 chinese amp's caps and resistors was a revelation.
one does not need to actually spend a lot on both the amp nor the caps or resistors to sound high end it seems. i wasted alot of money buying from online boutique capacitor sellers like hificollective uk (which i will post about soon, a different topic, once a great wonderful shop to deal with that morphed into a bunch of truly terrible people I want nothing to do with now)
power cords.
2021 definitely convinced me of their importance. i was skeptical before, but now consider them a critical part of any good system.