How important is the digital cable between the player and your clock ?

Garebear: Thank you for the additional details and 'Yes',...based upon several iterations of cables over the years, I believe that break-in for pure digital cables does matter and has to be undertaken.  The only exception (IMHO) is fiber optic (AT&T std) and TOSLINK.  SPDIF, AES/EBU and clocking cables all have seemed to benefit quite a bit from it in my system.

In short, yes, it's very important to get a good 75-ohm certified cable on the link between a player or transport and (if applicable) DAC and your clock.  That stated, you don't have to break the bank to do so but spending a bit more is definitely justified based upon what I've heard as I've tried these cables from several manufacturers.  I'm happy to talk in more detail offline however suffice it to say that when I went into the upper-end 75-ohm cable realm, I was rewarded with a bit more accurate timing/pacing, frequency rendering and sound-staging.