Subwoofer Speake Cable - Important??

I have a REL Stentor,and switched from the generic cable,supplied,to one from "The Cable Co".Cost was two hundred bucks.Made by XLO,and very well constructed.The difference was CLEARLY an audible improvement.NOT earth shattering,but more weight,and a better sense of air.Sorry,like me at first,it cannot be rationalized.

Your logic = degrading sound. A better cable will provide better sound.

I upgraded the Rel Storm 3 stock cable to an aftermarket version which is much thicker and has nicer connectors, etc. It looks great, and I like it, and am satisfied. I cannot say that I noticed a huge difference in sound, although I did not go back and forth, stock versus new and vice versa, to verify or refute this. So, maybe I SHOULD be hearing something that I'm not. I've no intention of running a bunch of "tests" to see one way or the other, though. Others HAVE claimed to have heard a significant difference with this upgrade, so I may be "wrong."

I think your logic is perfectly sound. You might test it by borrowing a
"better" cable, but if you're really objective about the comparison (or
have someone switch cables without telling you which is which), I'll bet you can't
tell any difference. Other cables, definitely yes. Sub cables, no, especially if
your sub does its work below about 50 Hz. Good luck, Dave

Of course you should pay attention to an appropriate bass power amp at first place. The Crown K2 is top class for bass and at a moderate price point.

The speaker cable for subwoofer makes quite a difference. I have – well had, as I’m just in the process to switch to a Maxx2 - the Wilson Audio WHOW subwoofer with the crossover point set to low 52 Hz, so you may think this is a small bandwidth and the cable may not be important.
I tried several cables – 3-4 ft. mono runs, starting from a 10$ standard cable, to a 100 $ XLO reference 6A cable, to several 1000+$ cables. I ended with the fantastic Elrod speaker cable, which is not only superior as a bass cable but also as speaker cable for my Watt/Puppy (where it replaced the twice as expensive Nordost Valhalla).
1100 $ retail price is high for a 3 ft. mono run, but matched with a first class sub like the WHOW, it’s worth the investment.

Bass gets more power and control, it sounds as it goes deeper with the Elrod.