This is a hornets nest and before answering I chose to wear my flame proof suit.
About 4 years ago I bought and borrowed 13 or so after market cables. These ranged from the HD650 stock cable to various costing over $300.
I "with my ears and my music" heard differences and two cables came on top. Funnily they were not the most expensive ones.
One of the cable manufacturers is no longer in business so I will only mention the Headphile BlackSilver cable as the one that opened up the top end of the HD600 while concurrently tightening the bottom end and flatenned the frequency response.
However, may I suggest that before you spend money on a re-cable you replace the foam in front of the driver (protects the driver) with a piece of stretched ladies stocking (new or used your choice
). You may find that said reversible modification is sufficient.