Thanks for some of the replies.
I'm curious about trying the direct into the wall VS. via conditioner in addition to trying some power cords, in a careful, sequential fashion as described. I appreciate the factor Erik mentioned about interference as a key factor.
I have heard power cords make a difference -- in a store. I do not know what difference it would (or could) make in my system.
Remaining skeptical until proven otherwise is my M.O. for this hobby, because there are many other places to make improvements. So, if I don't hear something, I will send things back.