Subaruguru, you wrote, "It's interesting to note that a very old junky-insulation house line, if dedicated, will sound cleaner than a new Romex one".
Fascinating! Because I am experiencing exactly what you describe. I just had two dedicated lines installed (10 gauge stranded as recommended by my electrician as what hospitals in So. California use to reduce interference). I immediately noticed a more forward sound in my system and was (am) panicked that the upgrade was not worth the expense. What you describe about the old wiring (mine is from 1941) sounding better is absolutely true, and if I wasn't hearing it for myself I'd never believe it could happen. I just hope, hope, hope with time...and hopefully a short time...the new lines will burn in and smooth out.
