Weak link

To refrain others, without a budget, photographs, and a room description/dimensions it’s hard to make recommendation on your solid system.  I would address the following, in the order listed, for both will have a positive effect on SQ:

1:  Power quality.  A good conditioner like a Shunyata Denali or Everest, or an Audience Adept Response T series.  Then, if your home design permits without much construction cost, dedicated 20 amp power lines.  If possible, one for digital and one for amplification.  
2:  Room Treatment. 

+1 @rikkipuu I never explored the grounding devices that are on the market but it is all a logical progression from good cables and power conditioning, to dedicated lines, to improvements in grounding to realize a reduction in noise in the electrical signal that I personally find exhibits itself as grain and hash that once removed results as richer timbre and improved liquidity, silence in backgrounds, and space evident between images.  I should probably add ground improvements to my next system upgrade.