Those External Audio Cards receive the signal in digital form, thus free of any noise they could pick up in the process. These are decoded inside the external DAC which then feeds audio to the speakers. since this part of the signal path is analog, any interference picked up by these cables is gonna appear on the speakers, which is why the good gear usually supports BALANCED SIGNALS so that the speaker can reference the signal and weed out noises added while in-transit.
My gear is a pair of YAMAHA HS8 speakers and a YAMAHA AG06 external audio card. Both support Balanced audio so that's what I'm using regarding cables between the audio card and the speakers.