520 quid?! Oh, man, I’m not going to guarantee results. Like I said, I have not had anyone else confirm my results yet. (maybe because getting 4 fuses is expensive at this level). And I did replace the fuses in the reverse order that you did: I changed rails first, then to the input power, and the difference was striking and immediate, with less perceived change for the mains fuses.
Good luck. Yes, the blue will work better than the OEM. How much better than the HiFi Supreme, I don’t know.
As far as valves, I got caught up in the Telefunken E88CC mess when my local dealer (Kevin at Upscale Audio here in the Los Angeles area) "found’ some Telefunken E88CC “NOS”. Now, Kevin swears by them. He tests every one, so we know they work and are quiet and perform very well.
But here’s the rub: 1) the boxes the tubes come in are too new to be NOS. They’re just too fresh and crisp, not what one would expect from a 50 year old tube box. 2) the lettering on the tube is the wrong color, slightly gold, and doesn’t rub off as easily as the factory Telefunken labels did. 3) Kevin’s supply of “newly discovered NOS” came after another batch had been out, folks were buying at $200 each or more, and found out they performed badly. 4) Some date codes on the tubes I bought match those on other suspected imitation tubes that were on the earlier batch that were skewered by the previous owners.
The tubes do have the “T-in-the-diamond” icon in the bottom of the tube in between the pins (But this could have been faked with a glued-on add-on pip with the proper molded logo) The pins are gold plated, as per the original.
But they test well, per Kevin. And they sound fine.
I suspect (but I can’t prove) the easiest answer is that these are real Telefunken E88CC, but used, and in this ‘new’ batch that Kevin found in Eastern Europe I think the fakers actually tested the tubes and picked out the good ones before they relabeled them, packaged them in new boxes, and then put 100 of them into the original 50 year-old packing box that was sold to Kevin.