Wow! Your description is dead on as to what my results have been. Isn't it interesting that "bassdude" and I have the same preamp (ARC REF-3), and yet we've gotten completely different results.
The first fuse I tried was an SR Red in the preamp. I was blown away by the results. Then, two days later I had my friend Robert over for a listen, not telling him about the fuse. All he knew was that I had made "some kind of improvement to the system." I left it up to him to guess what the improvement was. He guessed new cables, tube rolling, magic dust. When I told him it was an after market fuse upgrade, he wouldn't believe me until I showed him the box the fuse came in. He's a definite believer in the SR Fuses now ... and he is pretty much anti-tweaks and a real critic.
I thought geoffkait's Tice Clock story was interesting. I've spent an inordinate amount of time and money eliminating micro vibrations in my system. I'm thinking that that may have something to do with the outstanding results I'm getting from the fuses. The system was already (I thought) a very high resolution system. The upgrade to the SR Black fuses have brought me to the level you are experiencing.
Perhaps you're right in your assessment of moving the fuses in and out to make a-b comparisons. I'm hoping that mapman will leave the fuse in place for at least 50 hours before he gives up on it. It wouldn't surprise me if his fuse needs to break in all over again as it sat on my shelf for several weeks before I sent it off to him.
Al ... I have to say, you make this site very interesting indeed. Love reading your technical explanations. I don't understand it all ... but I do pick up some of it. I'm terrible at building stuff ... but I can sell the bejeezus out of it. *lol*
Crazy stuff for sure ...