My system still has a tendency to not sound as good during the week, I live close to some industrial units, the sound moves from sublime to good. It is nowhere as bad as it used to be and I have just discovered a simple fix that I am trying to get my head around.
If I disconnect everything and then replug it all back again the background noise significantly drops and the sound is back to Sublime I been trying this for the last 2 weeks and every time I try it I find I can relax deeper into the music.  
I think I am hearing a bit of noise residual and by disconnecting the devices and repowering I am removing the noise. Perhaps residual grounding noise?  
It seems a bit bonkers to be honest.