I personally still stand by the Cardas cable as my standard. Tried silver dragon, blue dragon, equinox, and some fine diy flavors. Out of all of them I feel the cardas is the most balanced with sound, comfort, price(excluding diy) and satisfaction. Avoid stiff and or overly thick ridiculous cables (those 18gauge monstrosities) because no matter how blingy and (in my opinion cheap) looking, they feel horrible on the head. I couldn't even stand 22 gauge in nylon types...
As for the sound, I personally can't say much between them because I don't seem to hear much difference, but I know I have top notch cables so it gives me piece of mind that it won't be the weakest link. Also avoid spliced solutions (like the equinox was)... I don't get what the hype is over that cable.
In the end it's up to you. Maybe for me I prefer cable from an established audio cable company, as opposed to some one man online thing built with diy-ish parts with a major pricetag- but, the only Best cable is the one you end up liking. As for the cardas/hd650 combo you can get it at
HeadRoom.
If you want to go thought what I did, then your best bet is to buy the headphones new then buy the cables used so you don't lose much money to try them all. Some mfrs also have return policies for the cable, so just try them and stick with the one you can live with.
Just my 2cents. I don't even hear the differences between reasonably made cables anyway. Curse audiophiles for building up paranoia and cable dependence