Ethernet cables

Just buy regular CAT6 cables you will never know the difference and for get that. Communications companies use CAT6 and 5 at high speeds in Data Centers without errors or issues. Spend your money else where.

Im of the belief that everything that you do in your system has the potential for making a difference.  Whether that difference can be heard or not depends on the resolution of your system.  Whether that difference can be heard and is worth the additional money is another story.  Every little improvement also adds up usually.  So adding a few extremely minor improvements can add up to a cumulative positive effect.  I use a 50ft run Supra CAT 8 Ethernet cable from my music server direct to my MSB DAC. Was it a major leap forward over my CAT 5e cable? Nope.  A very minor but audible improvement. But I also have a Tripp-lite isolation transformer, two Puron Power filters, and a GigaFoil v4 in the system.  Each made a difference, but cumulatively, It was a big improvement, say 15-20%. FYI, off-topic, but I found the Purons (my last tweak added) to make a startlingly significant improvement!

Sablon from.the U.K $400 a steal

Well made and well-shielded, not-junk ethernet cables are essential for carrying any data from point A to B. They need to meet modern standards too, as Ethernet speeds are not the same today as they were years ago. However, the stupid expensive ones are just that-- stupid. They are transmitting digital data not analog signals and will not sound better despite of all of the wild claims made by manufacturers. No one will be able to tell the difference in any true blind A-B comparison. So yes, a well-made cable should deliver data packets with fewer errors, which get corrected upon delivery BTW, but to equate the price of ethernet cables with sound quality is just more audiophile nonsense.

They are transmitting digital data not analog signals- False

If you tap into your ethernet cable do you see 0's and 1's?  You do not.  You see a square wave ranging from 5-80 MHz.  A square wave is.....wait for it.... ANALOG.  It is a wave.  It is shaped different than a sine wave but it is a wave.  It is analog.  Now since the square wave is interpreted at the receiving end as 1's and 0's it is not as susceptible to analog noise- ie. static and hiss, but the square wave's weakness is distortion causing timing and phase shifts.  And EMI or RFI can get in the line and ride all the way into your DAC, and that will affect the performance of a D/A convertor.  

No one will be able to tell the difference- False.  Better cables do a better job at interference noise rejection.  That is quite noticeable to the performance of D/A convertors, especially since lower cost DACs and music servers have little to no noise rejection on their inputs.  The higher end, more expensive DACs and Music servers have better noise rejection, isolation of the incoming signal and more often now, re-clocking.  At least they should.