This companies audio engineers seen to be dead serious about ubs cables -->http://bmc-audio.de/index.php/pureusb1-123.html I've never spent 400-600 on a cable but I do spend 50-60 on them and noticed a difference right away..
I can only say that to my ears the gold harmonix sounded better, others say it made no difference to there ears. It has been many months since I've heard the stock tubes from my WA7d. But I'm going to give my stock tubes a listen and find out all over again. My gut feeling is groovyd is right about the tubes & my ears are wrong..
Glad you mentioned this groovyd I suspected as much that really sucks for those of us who spent lots more money on the gold plated 6C45 from Woo. It also explains why I was never able to find these tubes anywhere else but from Woo Audio.