I can only speak for myself in this regard. The "placebo effect" may be occurring in your particular case (who knows?). In my situation recently I have re-inserted both the stock fuses and the SR 20 fuses. Easily the SR 20 is heard to be better than the stock fuse. When I return to the SR Red and/or the Black fuses, the improvement is undeniable, they are just superior sounding (the Black being clearly superior).
Not every tweak I've tried in past experiences has been successful, regardless of what they may have cost or my expectations.
In my case I can state without hesitation that the SR Black fuses are an excellent addition to my system. I can also accept that in your case the outcome is different for whatever the reasons may be. If the costlier fuses were only marginally better or just different, that's what I would report. That isn't the result of my listening.
Charles,