I do not have dedicated power lines for audio. But, I have used multiple 2.4KTopaz Ultra-Isolator trannis wired in balanced configuration, which halves the KVA rating. I had on/off switches placed on input side because unbalanced components will always be "on" in balanced config. All my Topaz are silent in 120V wiring and are placed in the listening room, right next to the components. There was no glaringly audible sonic problems with my power prior to their inclusion, I just added them hoping to get the more out of my system.
I have used a single TX for each amp and component (only because I have so many) and found no negative traits to their inclusions. In my system, there was no loss of timbre or macro-dynamics. The primary benefit in A/B listening was the old cliche of "blacker background". I didn't really know what background noise there was in my system/power until it was gone. The difference is subtle, but noticeable. All aspects of the music stand out more clearly against the quiet. I did try a power regenerator(forget the brand/model) ~8-10 years ago and did not like the result compared to balanced transformers
The effect of power transformers may be more apparent in extremely high efficiency horn systems, or high power amps which could be current-limited. But, my experience was better with them, than without them.