In my opinions cables are an essential ingredient in the thrill of realism in music reproduction. My cables including pcs, now represent at least half of the cost of my system. I really don't know where I might further improve my sound, but after the last four years, I cannot say where to try something new. And I should say that at my age I really hope I don't find one.
On double blind listening tastes, I have multiple times participated in them and think they are a complete waste of time as the mind is engaged in a completely different task during them than when we are relaxed and enjoying music. Psychologists using 30 second same or different judgments are wasting their time. It is an invalid measure.