Many of us use DDCs, a lot of them Denafrips Iris/Hermes DDCs. The benefit is most apparent when used with a modest streamer, some of that is that the DDC then allows I2S to be output to a DAC. I use a Bluesound Node 130 (with a LHY LPS), USB into a Denafrips Iris DDC, then I2S out to a Denafrips Pontus II DAC.
I won't go through every single SQ improvement, because in my system it improved every single part of the SQ of my streaming system; and allowed me to be happy using a modest system (and enjoy it immensely) while I save up for an Aurender/Innuous/Lumin streamer.
Will the DDC still be needed or useful once I install the new streamer? Possibly not, as others have suggested to me that it will not be necessary at that point....I'll let my ears tell me