Many years ago I did some work for a high end dealer that sold all kind cables including Nordost. Part of our agreement was to be paid in audio gear which he agreed to, at cost.
I acquired a full loom of Frey 2 cables including the QX4 and QB8. Now over time my family became accustomed to me breaking in speakers, buying and selling, etc. We had "game" of cable changing for a few months- one of use would change something and not tell the other- Purist entry cable or Monster. Most of the time after evening listening sessions the change would become noticeable.
I'd say about an 8-10% improvement from cables. Who cares if you buy them or not, but this is my experience from somewhat of a blind test.
I no longer have the loom. I ended up selling it for other upgrades and I'm glad I did. I can't say that spending the money matter- to some here $10,000 is a lot, for others it's a rounding error.

