Do you realize how arrogant this sounds? There are plenty of people with good ears and GOOD systems (many better than yours) who can't hear a difference when they reverse a power supply fuse or reverse polarity on an AC circuit.
Sorry... Its not arrogance. I and others witness to it. We have proven it by demonstrating it and its repeatable.
This may be the problem. You have to have not just one fuse changed. For, if half the fuses in a system are reversed? How are you going to detect only one being switched? It requires isolating and testing for each component's AC orientation first... and making sure all components are consistent to one another.
Then placing all the fuses in one direction. Then changing the entire system's fuses to the opposite direction. In the mean while? Having half? Or a third of the fuses opposed to one another? Nothing can be detected when only one fuse is reversed while too many are already hurting the system.
How do you isolate and test each component? Get a voltmeter. Ground the black wire to the outlet ground, or a pipe. Then test for the component chassis AC level with the red probe by touching a part of the chassis that is not insulated. I find on the bottom the bolt for a transformer works, or removing one screw from the chassis and touching bare metal. Some components have metal screws on the chassis that are not painted.
In the USA... You'll need a cheater cord - some cheap computer cord with the ground prong removed allowing you to plug it in upside down in the outlet.
Write down the voltage reading for when the AC cable is correctly plugged in.
Then turn the plug upside down in the outlet and note the voltage reading. The lower reading will be the correct AC orientation. Some components differences will be more extreme than others. When the lower reading is established? And, you find all units have been wired correctly? Then make sure all fuses go in in one direction as the others. The caps on standard fuses are marked in a consistent fashion. One cap will have the ratings listed, and the other cap with usually have a symbol or more.
That's just the beginning. Some fuse holders are snap in types at the IEC socket. Others screw into a receptacle. That needs some experimentation to determine how to get both kinds consistent in fuse orientation.
If all your components show the lowest voltage reading with the power cord plugged in as it should be? Without having to be turned upside down? Then you have something to work with in determining both fuse effect, and power cord effect.
Trouble is? Even very good manufacturers do not always determine the correct AC orientation. Why? I have witnessed to this with three high end pieces of equipment so far. One made in the USA. One made in Germany. And, one made in the orient. All high end companies.
Its frustrating to witness to.
When I find that kind of problem? Turning the fuse in the opposite direction to the other components fuses helps create a better balance in sound... though it would sound even better if the AC orientation was corrected to begin with.
With my "reputable" German made component, I had to go inside and reverse the AC wires that lead out from the back of IEC socket running to the on and off switch in the front of the chassis. It was hand assembled. So, I can see how someone might get that confused if they were very tired that day.
Having the correct AC orientation within a component does have a definite positive effect of the sound.
The other problem can be.... people buy cables to compensate for harshness. These will tend to dull the sound when things are being corrected.