I’m surprised just reading about it. Because while I have tried different grounding and heard differences they were never anything to do with wire type or gauge and the differences I heard were never anything like this. However, I have also seen so many experienced listeners like you hear things that, however unlikely really are there, that I no longer doubt these kinds of things. Because of this I would be looking for ways to understand what is going on long before I would be looking for ways to explain it away.
So just to get this straight Ozzy you are now running 16g solid (not stranded?) silver wire, from amp chassis ground, to some kind of star grounding box and then direct to earth ground?