I have a Blue Dragon cable for my HD650 and will say it is a quality cable that brings out more of everything the headphones are capable of doing. That I got the cable and the HD650 for about 50 bucks more than just the cable certainly helps.
Most people seem to prefer the Black Dragon to the Blue and Silver with just about all headphones. The Silver strangely seem to be geared toward specific cans. Moon Audio doesn't even make a Silver Dragon speaker cable; it's Black Dragon only.