Power and room acoustics are really really important.
After years of listening direct from the mains in an area with a highly corrupted electrical supply I installed a c.$6000 power conditioner which opened up the soundstage and lowered the noise floor, but as with all conditioners, there was some pinching of dynamics due to restrictions in current supplied to power amp during peak passages. I recently progressed onto installing a standard $600 (small fraction of cost of conditioner) balanced power transformer; soundstage expanded a little further, but now unlimited dynamics.
This change has NOT been subtle, so my advice is go for a cheap 4kV (at least) transformer to give your system totally balanced power and you will not be disappointed.
On the subject of room acoustics, I really object to dedicated listening rooms. Great if you have the real estate, but most of us have to live and listen in the same space, and you want to welcome, not banish the family.
So for me the SpatialComputer Black Hole anti-wave generator has been a Godsend.
With my current Zu Def2's they'd always sounded great except for bass node/standing wave issues esp. around the 27Hz region. Rather than redesign the room or load it with obtrusive traps etc., I gave the Black Hole a whirl.
It has really tamed these bass excesses so the whole musical spectrum shines. On acquiring the Def4's I am even considering one or two more units to totally subjugate this acoustic issue for good.
Happy to expand further on these issues, but total cost of c.$2000 has transformed my system, taking it to a level that spending 10x this amount wouldn't have acheived.