Unfortunately, fancy audio cards are almost irrelevant in the modern home audio environment.
If your video card has it, use HDMI instead. It provides 7.1 channels of high -resolution lossless digital audio, in PCM, Dolby or DTS formats.
S/PDIF provides only 2 channels of high-resolution audio in PCM format. For 5.1 surround sound, you have to use Dolby Digital or DTS lossy compression. It can't provide 7.1 audio.
If you use the receiver's 7.1 multichannel analog connections, you can't apply Audyssey room correction, bass management or any other processing.
Instructions for using the S/PDIF inputs (both coax and optical) of your receiver are provided on page 40 of your receiver's owners manual. It can be downloaded for free from the Denon Web site.