There is a designer from Sweden makes CAT8 and claims you can run it as long as you want. Supra Cables. Find them on Ebay. I got my USB from them and the noise I was used to disappeard. He twists the power leads and the data leads and adds a separate shield. In fact this cable made a bigger improvement than the ifi iSilencer+.
http://www.jenving.com/
http://www.jenving.com/