anyone upgrade their RCA connectors on Cardas RCA cables?

Yes, with even higher grade Cardas connectors up the line. You send your ICs to Cardas indicating which of the higher grade connectors you want, and they will re-terminate them for you, and install the next level up. It’s not inexpensive to do.

I re-terminated a pair of original the original Golden Cross RCAs with the new connector and design with the new install method they do now. It was more clear.   

The way they terminate, silver-solder, -or- some are crimp-only (no solder) can also impact the sound in different ways. Here is the link to the different RCA Males. 
You can call them and ask, and they’ll likely ask why you want to do this, fyi.      

https://www.cardas.com/rca-males

decooney, please elaborate “ways”.. also, any not biased data, such as blind test results, would be helpful! 

"The way they terminate, silver-solder, -or- some are crimp-only (no solder) can also impact the sound in different ways"

Cold welded vs solder some cold weld processes utilize silver paste which might be unique to Audioquest 

the KLE connector are intentionally LOW mass

imo those banging the drum for blind listening tests / results should fist ask the manufacturer about product development process that might include that. Failing that, why not design a robust experimental test and run it… peer review published findings… 

I was going to fix the spellcheck inserted fist, but decided it seemed more appropriate 

To @westcoastaudiophile the physical differences I’m aware of are more mechanical in nature, and less measurable, negligible, as I understand it. Even Cardas will state they have cables that measure the same and sound different. I’ve experienced this myself, two pairs of the same, side by side with different type connectors/connections. If you can’t hear a difference, it does not matter or makes no difference, to each his own.  

Clipped Notes:

• Contact Resistance: High-quality crimping, often referred to as a "cold weld," can achieve extremely low contact resistance—typically less than 10 mΩ—an airtight, metal-to-metal bond. .
• Impedance Consistency: In high-frequency or precision lab environments (e.g., >18 GHz), soldered connections can sometimes offer slightly better return loss or Voltage Standing Wave Ratio (VSWR) due to more predictable and consistent resistance levels.
• Mechanical Strength: Crimped connections generally offer superior vibration resistance and mechanical durability, as soldering can create a "brittle point" where the stranded wire meets the solid solder.
• Signal Loss: For most audio and commercial RF applications, the difference in insertion loss between a properly executed crimp and a professional solder joint is negligible, often measuring less than 0.1 dB.