HAVE CABLES EVER TAKEN YOUR SYSTEM FROM SOUNDING JUST OK TO SOUNDING GREAT? Experiences ?

Yes. No doubt, sometimes huge.
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The dramatic improvement happens only when you change stock power cable of your amp to hi-fi cable, even not expensive. Later, if you hear a huge difference between two hi-fi cables, I think means, that one of them is dummy.

Yes. When I added Iconoclast Series 2 TPC speaker cables, the upgrade was dramatic. My boss called out from 2 rooms away to tell me that whatever I did, the system sounded much better. Later, she even turned the system on herself to sit and listen, which is rare. And the true test: She didn't start by asking "how much did it cost?" After she approved, I nervously asked if she wanted to know the cost. She said "no, it was worth it for that kind of improvement". (!!!)

Another big cable improvement was the Tubulus Concentus v.2 I2S cable btwn. my Jay's transport and PS Audio Stellar Gold DAC. Sublime!   

Yes, but not the ones you sell,

 reducing the noise floor in the cabling and equipment you have a better listening experience.

Agree if that is one's sonic target, it's an expensive endeavor with few with sufficient budgets to cover.  Also great if one can lower ambient noise, like in a dedicated custom treated audio room