Hi There You appear to be using the Marantz SR7010 as just a preamp / processor and using the Emotiva as the power amp(nice setup). Don't bother with a sound card, you simply need to connect the pc to the Marantz via HDMI out from the NVidia gtx 1080ti to one of the HDMI inputs on the Marantz. You then need to configure the HDMI settings on the NVidia card to bit stream to the Marantz.The Nidia card should be able to support Dolby DTS, DTS-HD, True-HD etc. The Marantz will then do all the decoding.
Worth having a look here for info click here not sure any currently available sound cards can transmit HD audio.
Regards Keith W