My solution to the nest of wires (I have the Hegel H20 amp) is to seperate all interconnects and speaker wires from AC cables. I put that black foam pipe insulator with the slit in the middle (cut into several pieces) to seperate all the low power interconnects/speaker wires from AC cables, just slip it over the interconnect and AC cable, cheap and effective.
Sounds like either a combination of cables picking up AC and/or DC gettting into your power lines, several products out there to clear up DC on power lines which make transformers hum as many have noted.
Your system is deserving of power conditioning, I like the Puritan PSM136 conditioner with groundmaster and some Verifi audio plug in thingies, astounding how much improvement that comes from cleaning up the power.