Hi end audio would be any recent motherboard with a spdif out port. The realtek chips do not do anything with the audio when you set them to spdif/optical out. They send the stream straight out the port unmodified. Connect to external amp with a DAC and your set.
I am someone who used to use dedicated cards from M-audio, cirrus logic, Envy pro cards but with the way the current chips handled digital out there is no need. Just make sure you do not enable the eq, or any of the processing features as that will cause the audio to take a path through the chip and be altered vs going straight out the port like the source.
Here is how the realtek chips map digital, notice the difference in analog and how it goes through lots of filters, etc. The bus between the chip and the host cpu is natively 48Khz so if the source uses that then it is bit perfect. If the source is 44,1Khz or 192Khz then there is some slight, very slight bit altering to make up for the difference because it has to sample the bus at different intervals to keep the clock correct . That isn't a realtek thing , it is the HD audio spec that sets that rate. It is about a .01% difference, but knowing how picky some people are they will claim they can hear that