Well I don't sit around here and make this stuff up.
I made mention of the PCM output... which your PC does natually, as my FIOS HD cable box made by Motorola Q6200 doesn't output the audio data in PCM format. I found this out accidentally on purpose, trying to do one of the things you noted above not too long ago myself, Hooked it up... and got nada. Spent two days calling Verizon FIOS support and even Motorola support... again... nada. None of the support teams even knew what PCM was/isw.
I then called the support for the DAC I had at the time and sure enough Lavry Egn. wsaid as much too.. ONLY PCM. Bel Canto was up next and when I finally got to them same thing. PCM.
Lavry's DAC converted higher sampling rates to 192, vs. BC DAC3 at only 96 via TOS or Coax inputs, and only 16/44.1 K on USB.
SO THERE'S ONE MORE CONSIDERATION... IF usb IS USED.... insuring the output stream is within the parameters of the DACs abilities for each interface... USB or Coax. Likely it will be if you are streamning audio off the net. My Bel Canto DAC3 will via USB.
Lastly, the interface is key... USB TOS or Coax, as much so as is the prospected DACs abilities.
BTW be mindful of the numbers game... 16/44.1, 16/48, 24/96, 24/192, etc. more or larger numbers might not correlate to better, and some DACs don't upconvert to their analog outs. They merely process the info given them... ala BC DAC 3, Lavry DA10... ETC.
i SAY TOO... "If you like what you are getting, keep doing what you are doing.... if not, then change what you can."