A few OPINIONS on three of the suggested changes.... These are opinions based on my experience. Others have probably had different experiences. YMMV.
A nice and effective room treatment is just the addition of a lot of artificial plants. Doesn't have to look like a tropical rainforest, just break up the reflected sound. Will make a big difference and help reinforce the WAF.
Vibration / isolation can be easy and inexpensive. Vibrapod cones are very effective. Maple butcher block works and looks nice. A combination of Vibrapod cones and maple butcher block boards can make a difference.
In my opinion, power conditioning won't make as much difference as an improved phono stage (1), room treatment (2) and vibration control (3).