Simplest and cheapest option: buy an inexpensive TOSLINK (optical) cable and connect your PC to your NAD with that, as
@respice finem advises in the comment just above mine. If that optical output is not from your PC's motherboard but rather only available on your PC's soundcard, then of course you will not be bypassing the soundcard. But with optical, who cares? As noted above, there's no ground/noise issues to worry about with optical.
However, as has also been noted, a very long run can produce dropouts (or I suppose in some cases total silence) over an optical connection, especially if you are looking to stream audio with sample rates above 96kHz. In actuality, sample rates higher than 96kHz usually work just fine with optical - not to mention, there's no point in using sample rates that high anyway.
But if you are concerned, or if you have other reasons you'd prefer not to use your PC's optical output, then I'd heartily second the above recommendation for the SMSL PO100/100 Pro. I have the 100 Pro, but only because the regular 100 happened not to be available when I need to purchase this kind of device.
My 100 Pro sits between my Mac mini and my Genelec active speakers. The signal path is Mac mini USB output-->PO100 Pro-->coax-->coax to AES EBU cable-->Genelec AES EBU input. I've never had a problem, and this is using the PO100 Pro's coax output, which theoretically is susceptible to noise, gorund loop, and so on. In fact, my "digital coax to AES EBU" cable is actually just a cheap Monoprice analogue RCA to XLR cable, and it works just fine (albeit my cable run for that is only 6 feet). The PO100 sits in the back of a cabinet and I can't even see it - it's literally out of sight, out of mind and just works.
In your case, using the PO 100 (or 100 Pro) optical output would eliminate the theoretical concerns of my setup with its coax output and the "wrong" resistance on my converter cable going into my Genelecs. So I'd say your setup would be bullet-proof unless you tried to run 384kHz sample rate data over a 20 foot connection or something silly like that.
Oh, and for my use case - and therefore for yours too - the PO100 and PO 100 Pro are functionally identical, so if the 100 is available again now, no need to spend the extra money on the Pro.
