I found my problem and resolved it, and it had little to do with anything I thought of in the past.

I noticed that one keyboard was flickering on and off when I played it. I decided to change out the power strip. That power strip had 3 keyboards, a tremolo/Leslie effect stomp box, and another power strip that only the Wharfedale monitors plug into. When I changed out that power strip, I took out an older generic strip and put in one that has an indicator on it when a line fault is present. As soon as I hit the power button, the red fault light came on. Reset the strip, red light stayed on. Took that power strip to another outlet on another circuit, no red light. So I ran that power strip from a different wall outlet and now everything is quiet. So bottom line, the problem in MY case was a bad wiring job inside one of my walls, not surprising given what else I inherited when I bought this house in early 2009. NO ground lifts, no re-routing, just a bad wall outlet. Fortunately that wall is going to come down anyway and I will just eliminate that wire run.

But yep, everybody who said it was power conditioning for the few of us who talked about AC related hum was right on it.

And now back to the Stanley Cup game.....