The DAC on the Marantz is most likely the best but the best way to tell is connect the soundcard to the marantz via analog cables and then via a digital and see which you like better. It is strictly a matter of opinion.

Regarding cables, IMO at this level the cable is not that critical. Your speakers and amp aren't revealing enough for this to make an enormous difference. A quality DAC will do more than cables ever would to improve your sound.

HGavrilov wrote:

Hi guys! I have the following devices: An old laptop; Creative SoundBlaster Omni 5.1 USB external sound card; Marantz PM6005 amplifier; 2 Q Acoustics Concept 20 speakers. The question is, what is the optimum wiring to get the best possible audio quality of this setup? The speaker cables at the moment are Cambridge Audio, mid range cables. The external sound card to amplifier is connected by Atlas Element Integra cable. Any suggestions on whether the sound can be improved furher? Also, I'm confused as to which DAC would be best - laptop (unlikely), external sound card, or the amplifier itself.

I'd be inclined to first try the optical route.