Ethernet Cables, do they make a difference?

LOL, no. God I swear if I see anyone chiming in or trying to hock an "audiophile" Ethernet cable, I'm going to lose my lunch. 

You're off to a great start on that 9th post. 👍

I'm speaking of the efficacy of parlor tricks vs. listening.

What is it that you propose to test?

What ever it is that allows someone to take a $340, 1 meter RJE cable, an declare all sorts of sonic bliss. 

It's what I and others have repeatedly stated: long term listening is the correct way to identify sound signatures and clues. You can get the gist of a cable or fuse or what have you but it takes immersion in the music, over time, to correctly assess anything, unless it's something glaringly apparent.

Great. Love it. Then I will setup a server/client/switch where there will be power going into the black box, a USB port on the output side and a Cisco Switch were I can issue a shut/no shut on FA 0/1 or FA 0/2 and turn power off to that port. 

The client will have a dual port NIC in a LACP Passive LAG (The switch would be port channeled and LACP Dynamic LAG). Use JRiver in WASAPI exclusive mode or ASIO depending on the claimants DAC and we could literally collect data for a 1-6 months EASY.

They would never know when the shut/no shut on either FA 01/ or FA 0/2 would have been made therefore they wouldn't know which Ethernet cable was in use. 

You could do that. But why not swap cables in someone's personal system that he/she's intimately familiar with?