Hard to believe all the crap that flows thru an ethernet cable

So apparently lots of crappy stuff needs to be cleaned up from your ethernet cable before reaching a dac.  
And to thoroughly clean it up you are wise to spend $1300 for an optical rendu device, and sound quality drastically improves.  Wow. Sounds like a great deal.  
I guess a really good dac with galvanic stuff going on and strong pwer control needs more help.

do i really need a rendu device? I see it on high end systems so that seems good.