I once heard a very interesting talk by a John Camille on what it would take to achieve 60, 70, 80, 90 and 100 db of signal to noise. His conclusion was that 60 and even 70 were doable. That 80 was achievable with great difficulty and that 90 could be achieved only by impractical means such as encasing components in half inch thick steel with no holes anywhere! 100 db was, he said, God's country.
I have found that charged cables are a very great improvement at least in our modern world with all the EMI and RFI around. I suspect that were we to put everything into a Faraday cage, we would all hear an improvement and listening in a room that was a Faraday cage would be better yet.
Yes, Scott, I suspect better isolation and a grounding plane would make some difference. I think putting one on top the unit would also. But would it be very great? I don't know. Long ago I realized that isolation was important also, and I experienced modest improvements. Later I was shocked at the improvement given with the SR MIGs and even more by the StillPoint Ultra SSs and Ultra Fives. This was well beyond what I thought was possible. All that I will conclude now is, "try it!"
