fuses - the $39 ones or the 85 cent ones

Don't hold back, Musicnoise!
One bit of science you missed is the idea of repeatability.
When I add 2 plus 2, I get the same answer as anyone on the planet.
When you take a match to a balloon full of hydrogen and oxygen, in the proper ratio.....BOOM, you get a little puff of water vapor....every time.
There are various ramifications of all this tweak stuff.
That there is no concensus about anything...even as simple as a fuse, for Pete's sake, is a sign to me of extreme subjectivity and Weird science.

I am building a Faraday Cage around my house, even as we speak. I'll have 10ft Copper Ground rods driven by the end of the weekend and borrow a 'megger' from work to test the resistivity of ground. I'm sure this will remove the last bit of remaining haze from the upper octave.

By the way, if I am mistaken as to the location of the fuse of which you speak, and it is indeed neither a line fuse nor, for that matter, a fuse for one of the rails, then it makes perfect sense that the gold endcaps would make a difference. I was just not aware that any amplifiers used fuses to protect a differential input stage. I would highly suggest that you replace both of the fuses at the same time and purchase only a matched pair.

Musicnoise, your theory does not apply here in highend audio.
The only explanation is what you hear with your own ears!!
Whether it can be explained scientifically, mathematically or otherwise means nothing if you can't hear a difference with your own ears. The proof of science cannot change my hearing!! or what I percieve I hear.

Undertow, I wasn't aware that Krell went out of business. Where did you get this information?

I tried some of the premium fuses in my Accustic Arts transport and DAC (not tried them in pres or amps) and I cannot tell the difference, but I'm 50; maybe one needs to be younger. All the same, they seem well made as far as fuses are concerned, but I'll be sticking to sand filled ceramic types from Roger Modjeski, not that I can hear a difference, but for $3 I don't care (as much).