Legitimate differences are most reliably heard at home in one's own system. And there, if I can't hear the difference between two pieces of equipment from the next room (and better yet, from down the hall), then the proposed upgrade is generally not one I am interested in. There may come a time that the improvement can no longer be heard that easily, though I haven't reached it yet. When I do, I hope I realize it is time to stop.
Not surprisingly, I find the differences in cables and interconnects are more subtle. For that reason, along with others, I am not likely ever to be a promising victim for the wire bandits.