Received my Silver Dragon v2 cable for the HD650 this morning after only a week from ordering. (Well two weeks actually, but air traffic was down due to the volcano in Iceland.)
I can tell you the change in sound for a HD650 with this cable is dramatic!
No psychological effect, just listen to a song you know well with your original cable, switch cables and listen to the same song again. It's clearly audible.
The famous Sennheiser veil is gone, bass stays as full and low as before but it is totally cleaned up and has a fast attack instead of being muddy.
Agreed, the cable isn't cheap in relation to the price of these headphones, but if you love your 650's it's well worth the money. And there are more expensive cables out there.
I have a couple of other phones that might really benefit from a recabling job.
As soon as all the stuff I ordered recently comes in and some older amps are sold I will use the money from the sales and get them all recabled by Drew.
One hell of a cable Drew!