Not sure if useful, but another source for Supra
https://www.madisoundspeakerstore.com/cables-and-interconnects/I had heard their high end ICs are nice, but never heard them. The only experience I have was when I upgraded my HR-1s. I feel sure Bob was using the 15# Supra Classic Speaker wire for internals then, but I can't remember where I put it%^&*(. I liked it, finding it nicely colored. As I recall it had a somewhat "tubey" character, balancing some toward bass, but also with a tin on copper "glistening" detail effect that worked through the fullness enough to have a sort of classical "warmth." But for me it finally felt a little too dark, slow, and colored. I ended up with all Neotech UPOCC copper wire, but I was already partial to Neotech from making ICs, power cords, and for amp internals. It is just the most transparent and speedy wire I have found that I am willing to pay for. If anything, it is on the clear side but good at being "not there" to me. Changing the Supra Classic wire, which looks good on paper, to Neotech UPOCC, was like lifting a sheet off the speakers. Now this was only one stock low cost Supra wire, but my experience. I find it a challenge to get clear on anything without comparative analysis, especially when so much opinion is based on our always different systems and rooms....
A present example for me, I have never loved Sophia 274B rectifiers... I liked most everything about them, but never fell for them fully with my Torii MKIV or CSP3. They had a slightly intellectual feel for me. Lately I am playing with a used, nicely modified 300B amp that surprised me in how overall similar it felt to where I had gone with the Torii. It came with nice tubes, EML 300Bs, a Ken Rad 6SN7/VT-231 input and Sylvania 6BX7 drivers. 5U4Gs are the standard rectifier for the amp, he sent a nicely transparent pair of maybe 60s RCA 5U4G-STs. But for me, all else the same, the amp needed better speed balances, a little tighter bass, and less roll off/more fine detail.
I changed to very transparent and fast CSP3 tubes which might have been too clear with my MKIV, but this made most tubes work well in the 300B and the amp started showing its beauty. I still had to explore a little with different tube combinations for a relatively complete musical balances and the spacious and musical lucidity I need ... where the amp disappears for me.
Then playing with the 300B amp rectifiers, I liked a lot of the 5U4Gs I tried pretty well, but the Sophias were sort of in another league. They just did it all right for me, great balances, adept, friendly and rich with just enough added touch of clarity and fine detail to open and let the amp sing. With it, quite a few input 6SN7s and both pairs of 6BX7 I have work pretty easily toward variations of complexity and balances I am after in the 300B. I have found beautiful combinations, and the Sophia 247B, which I did not love in the Torii, in this case had a lot to do with making that happen. In this amp, in my system/room, now I could say it is an excellent tube.
It is all so amazing, how so much of what we do depends on synergy. It also always amazes me how no matter how close to real the system and room make music, seems it can always gets better, seemingly without end.