The most transformational equipment change I made was replacing a Rega tonearm with a Basis tonearm.
The most transformational change I made to my system was installing room treatments.
That Transformational piece of Gear We All Wish For
I suspect most of the music/audio lovers on this web site have wished for that piece of gear that literally transforms their system? I know i have. I have been going down this audio rabbit hole since the mid 70’s, and there have been a few pieces that made a really nice improvement to my system (the PS Audio P20 Power plant being one of them). However (and this comment only applies to pre-amps and amps and no other category), nothing that I can ever recall has so energized and improved my system in so many ways as my new pre-amp. I have owned some really fine brands in the past including Pass, Coda, ARC, PS Audio, Rowland, and more, but now I am a BAT Man for sure. The new pre-amp is the BAT VK-80 and I love that beast. I hope everyone reading this will get a chance someday to try one in their system. I know he is a controversial figure, but Kevin Deal's review of this piece is so right on. He really loves it too and rightfully so. https://www.youtube.com/watch?v=Iv2swa55JXo
My system consists of:
Thiel 3.7 speakers
Coda 16 power amp
PS Audio DSD DAC MK II
PS Audio Perfect Wave transport
PS Audio P20 power plant
BAT VK 80 preamp