I have used the Neutrik Profi - they are garbage in terms of sound quality - I have a bagful to prove it. The newer range of Klei are a new design and better than the earlier Eichmann bullets. The Klei and WBTNextgen are both good sound wise, and I have used them. Nevertheless I prefer a vintage plug from the 80’s, lightweight, minimal metal and robust.
With regard to the WBT’s - one of my preamps had Nextgen chassis mount RCA male sockets - the surface coating has long gone, whereas the other RCA’s for the other inputs are still like new. I question their longevity.
PS I used to distribute WBT’s in the 80’s and their quality control at the time was appalling.The centre pins on the original RCA’s were very short and on many top end components the WBTs could not actually make proper contact.
The Eichmann chassis mount RCA male sockets I have installed on my Marantz tube pre - they are ok sound wise, but no better than the original teflon/gold I had installed 25 years ago.
As far as cartridge pins go - the Cardas etc are garbage. I prefer sonically cartridge pins that are phosphor bronze base rather than the tinny brass used by most, including name brands.
Best connectors are copper or silver body ( no brass ) and minimal metal and non internal joints. If you are in the habit of melting Eichmanns or Klei’s then I suggest you go to soldering school and learn how to solder properly.
I have no experience with the Xhadow apart from 1 pair of interconnects, which, after about 4-5 years, the connector surfaces were tarnished to eternity. Not very impressive on the longevity front, given the cost..