What one change to your room, system, or setup made the biggest improvement?

In descending order:

Acoustic treatments

Electric quality

Decoupling products

My recent moment ahha moment has been moving my subs from behind my speakers to closer to the side/end walls, thus allowing me to lower the crossover point and the subs volume.

ozzy

Great post! Hard as it is to pick 1, I’m going to have to says adding the DENAFRIPS Hermes DDC in front of my Pontus II 12th DAC was it. I just could not have even hoped it would have made the improvement that it did. Amazing! 

in rank order (7 very significant drivers of high level sonic performance)

1 - building a dedicated room

2 - treating said room

big gap

3 - magnepan 3.7x with rel subs

4 - lampizator dac

another big gap

5 - grimm streamer (mostly stream these days)

6 - lan cleansing for streaming

7 - well tempered labs tt / dynavector cart

A tie: Holostages and Telos QMT