I want to send Dolby Digital 5.1 surround sound from my computer (playing a DVD in VLC, or an OTA HDTV broadcast in Microsoft Media Center) to my home theater receiver. Since I do not have an SPDIF out port on my motherboard, I plan to add a sound card with either Digital Optical or Digital Coax out. If that is all I need (in other words, I will not be connecting the analog ports of the card to any speakers), should I just get any cheap card that has a SPDIF port? Do all cards (cheap or expensive) spit out the same signal from their SPDIF ports? Are they just passing the Dolby Digital signal through untouched, to the receiver? Do bitrate and sampling of the card (16 bit 48 kHz, vs 24 bit 192 kHz) affect only the analog ports, or does it impact the SPDIF port as well?
For example, is there any functional difference between these cards, if just looking at the digital output?:
PPA 1431v 6 Channels 16-bit PCI Interface Sound Card
NewEgg Item=N82E16829126005 (Forum will not let me post URLs until I have 3 posts
PPA 1424V 8 Channels 24-bit 96KHz PCI Interface Sound Card
ASUS Xonar D1 7.1 Channels 24-bit 192KHz PCI Interface Sound Card