I recall replacing Silver Surfer XLRs with WireWorld Platinum Eclipse 8 - HUGE difference in quality. Im not inclined to A/B them at this point, though, it might eat at me. However, I used a sample Nano 45 graphene contact enhancer on the WWs, and can’t find the rest, so I assume that would skew the A/B
FWIW you can have an entirely differential balanced preamp and it may not support the balanced standard. If you hear differences like you describe above it probably doesn't.
Back in the 1950s in the Golden Age of Stereo a great number of remarkable recordings were made. They still sound great today- and the better our systems get the better these recordings sound. They have the kind of neutrality that they do largely because the balanced line system is an exotic cable technology- but instead of spending the money on the cables, the money is spent on driving them and handling them correctly so colorations are eliminated.
Cable manufacturers hate it when I talk about this! That's because if the standard is supported in your equipment, its very difficult for them to make a sale if you listen to what your ears are telling you.