About a year ago I was experiencing system symptoms virtually identical to those the OP has described. At some point after much thought, frustration and experimentation, I replaced my speaker cables and the harshness disappeared.
30 feet of Monster Cable or 12 gauge TW cable from the hardware store will be an easy and inexpensive experiment. Hope this helps.
30 feet of Monster Cable or 12 gauge TW cable from the hardware store will be an easy and inexpensive experiment. Hope this helps.