When I switched to a dedicated 20amp AC line (with 8 awg wire) for my DAVE directly feeding Utopia,I immediately heard more low level detail but the most noticeable difference was the removal of harshness in the highs. This makes me believe that noise was making it into the DAVE and causing harshness. Harshness I didn’t really notice was there till it was gone.
I realized how noisy my AC lines were at my old place when I was listening to music and ran my paper shredder which was plugged into an adjacent wall from the DAVE, and I heard all this noise and static from the shredder bleed through to the headphones.
Now, if you have a fairly new home with good wiring, the jump to a dedicated AC line might not be as big as it was for me since I started with such crappy AC.