XLR cables for a reasonable price?

Blue Jean.  Nothing special as in not magic. Just a good cable. 

FWIW, unless you have transformer outputs, your XLR outputs are not balanced. Close and good enough but not balanced.  Parts tolerances and just plain old Physics.  If running over about 3M, I would use them though even with their much higher capacitance than good coax.  If you want to really understand this topic, I would refer you to the Jensen transformer white papers. 

XLR to RCA is not too bad, but RCA feeding XLR is going to give a gain miss-match causing maybe higher noise. Many of the adapters are made incorrectly so be careful. 

SOME XLR is louder, some RCA is louder. This is where we have some issues with specs.  I thought XLR was pretty well-defined in the professional industry but it seems a lot of consumer products do not follow those specs.  Seems they don't even respect the 600 Ohms spec. In consumer it varies from 10 to 50K. That is one of the specs you may trust from ASR.  All that may make interconnect parameters matter more as big differences in current. 

Morrow doesn't upcharge for balanced.

I would like some recommendations on reasonably priced XLR cables that give excellent sonic performance.  

“Excellent sonic performance” doesn’t really help as we all hear and value certain sonic traits differently.  What specific sonic characteristics are you looking for, what are you using now, and what improvements would you like to achieve?  This critical info will get you much better recommendations more targeted to your specific tastes.

I have had my XLR cables made up by ProAudioLA (a pro-audio shop in Los Angeles) for years now. You can have them made with Neutrik XLRs and Mogami W2549 cable and will be hard pressed to get better results than that. Similar cables are now sold on Amazon by a firm called "World’s Best Cables." I prefer ProAudioLA, as I can have the cables made to the exact length needed, with the exact color-coding needed, and I'm supporting a local small business. Whatever you do, I hope you have a ball!

P.S. Because I use long XLR interconnects, I was only able to get one (well-known) audiophile manufacturer to let me try their cables. They were noticeably colored compared to much cheaper ones from ProAudioLA. So I saved about $1,400 on that pair.

@soix Currently, I am using a Primaluna integrated tube amp.

However, I am transitioning to a fully balanced system, with Atma-Sphere MP-3.3 preamp and Atma-Sphere Class D amps.  
These components, as well as my source components (DAC and phono preamp) are fully balanced.

Just wondering if it is necessary to buy ultra-expensive XLR interconnects to get the most out these components.

My speakers are Acoustic Zen Crescendo Mk II.