DDC effectiveness generally with I2S, I2S input on many dacs allows local or host clocking, host or DDC clock may be superior to dac clock. I don't see the point of adding DDC for usb unless streamer usb really poor.
I agree with prior poster in regard to diy builds, many levels of performance depending on build.
How can you argue with people who claim to hear no difference with dedicated streamers vs multi purpose computers, they get to be happy without any extra expenditure. For those who've not heard a dedicated streamer in their system speak from experience rather than rehashing other's experiences.