IMO,it is certainly worth upgrading the cable from the DUM, especially with the top flight equipment you mention. As I've said previously, the DUM cable is a very very good cable for a stock cable. But that doesn't mean it can't be improved upon. When I went from DUM to WyWires Red the sonic improvement was obvious in a few seconds. More of everything, tighter bass, clearer and more detailed mids and treble. So I put my DUM in the box and never took it out again. And when I went from the Red to the WyWires Platinum, there was, again, another obvious big improvement, I would say an even bigger improvement than when going from DUM to Red.
To me the improvement with the upgraded cable was quite significant, almost akin to changing a another component.
Dan uses high quality cables in his shows, including CanJam, for a reason: they make a difference.
But I must say that if I never upgraded the cable and used only the DUM, I would still have been overjoyed with the quality of the Ether Flow (and would not have known about or felt a need to upgrade the cable.)