Ever downgrade and have better sound?

Many times in last 40 odd years, My house looks like a cable factory. I never throw one away, what sounds terrible in one set-up will sound great in another.

I agree with Schubert. Many times for me also, not only with
cables, but equipment too.

Not very often, but it can certainly happen very easily.

Strictly a judgement call in my case, but I preferred my small $500 Triangle Titus speakers to B&W P6s I owned prior that cost almost 4X as much.

Accessories (I consider wires to be accessories) are a different story. IT is hard to predict what will work best until you decide on something and try.