Thanks Djcxxx. Your comments kinda' substantiate my general reactions that at some point, there are diminishing returns.
I used to own the Ref 3 too. I had the same reactions as did you about the change from the Ref 3 to the Ref 5, and then again to the Ref 5 SE. By the way, for the benefit of those folks who own a Ref 3, let me assure you, IMO, it's still one heck of a great linestage. Sorta' makes me chuckle when I read that going from component A to component B will be a "day and night difference."
As I mentioned elsewhere, I may be going down upgrade alley again, but this time with speakers. Paradigm S8s to Vandy Quattro Woods, maybe?? Reason: I have agita that the S8s may not be a good electrical match for my ARC tube amp.
The dealer will drive the Vandies with the same ARC tube amp that I own. Now that will be an interesting audition.