Do Costly XLR Cables Make A Difference?

“…for dedicated audiophiles who sometimes change their equipment, it is good to treat a selection of cables as tools in a tool kit for final tuning.”

@jjss49 

I agree, and with the rest of your post too.  
The cables need not be expensive but it helps if they are different and bring their own unique strengths.  For example, I keep SCs by Harmonic Tech (lots of OCC copper, fine gauge solid core, and individually insulated), Furutech (super fine strands of OCC copper in foamed PE), and NOS WE (annealed, tinned, stranded copper), and a few others that all result in a subtly different sound.  Same type of deal with PCs and ICs.

I recently switched from Audience Front Row XLR cables (between my Audio Research CD9 DAC and my Hegel H390 integrated amp) to Snake River Audio XLR cables. The SR's are cheaper than the Front Rows, but there was a nice gain in sonics - more dimensionality, better clarity of images, better audibility of air both in front of and behind the images

I’ve heard plenty of difference in single ended cables, both good and bad. I’ve never heard any difference between balanced (xlr) cables in my system. 

very simply, do an honest (blind) A-B test on this. i'm willing to bet any amount of money that there is no detectable audible differences among properly-built, well constructed cables. amazon basics, monoprice, world's best cables are among the low cost choices that i have used repeatedly. there's snake oil nonsense and then there's audio cables nonsense. feel free to flush money down the toilet if it makes you feel better somehow ... no one is harmed except the person throwing away his hard-earned money.

again, just invite a few friends over and set up a truly blind listening test. at the end of the day, isn't the sound quality what we are after? why pay for things that simply do not sound better? save that money for buying records, upgrading speakers, etc.