There has been some mention that 1.5 meters is the best length for a digital cable due to the fact that it is a multiple of the wavelength of the carrier frequency of the digital signal.
I have looked at different lengths of digital cables on my scope and with longer lengths I can see overshoot and ringing of square waves. In my opinion, the shortest length you can get away with, with ANY cable is the best.
I have never heard from Eichmann that the Silver Bullet should be used
only with silver wire
There are quite a few folks on this forum who use the digital cable with Silver Bullet Plugs. There is a subtle difference and improvement using a pure silver connector. As to if it is worth the difference, you are the only one who can make that determination.