Bearing in mind you don't seem to be located in the UK some of the prices quoted won't make much sense for you.
I would say you may find a better deal looking over at head-fi.org forums where there are some cable makers who will make one up to a good standard for a lot less than the main commercial ones.
I've got Zu Mobius on my 650s but I've seen it stated that the 600s are better with Cardas though I've never tried Cardas myself.
A good site I have used is
www.headphile.com, I've had 2 sets of grado headphones upgraded (wood eearcups and recable) and he has an excellent rep over at head-fi.
I presume buying from US would be easier for you.
Steve
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