From what I have gleaned over time on this topic, the main objective is to end up with the smoothest, most regularly shaped curve to the cable run between the digital components. Depending on how the transport and DAC are positioned relative to each other, it would make no sense to purchase too long a cable and wind up with extra bends or loops in the cable run. Conversely, don't buy too short a cable and cause sharp bends at the connectors with the cable pulled straight in between. Let the physical setup of your system dictate the correct digital IC length.
