I have owned a few dacs with a built in streamer. The dCS Bartok was pretty good and I found that the Ethernet input was the best sounding input. I also ran this Dac directly into a Krell duo300xd to good results.
I have an MSB premier with their network renderer card. This input is really great it is an additional cost but I find it well worth it. I took a leap of faith and bought the gigafoil and an ifi lps to put in line between my roon core and the renderer. This is the best bang for the buck upgrade I have made. I actually brought the gigafoil and to my dealer friends shop and we tested against the Innuos statement with an MSB reference Dac. He listened back and forth with out hearing my thoughts and was shocked. The gigafoil was so close if not better than the statement that he bought one for the store. He now uses the renderer with a gigafoil and the Innuos sits on a shelf not being used.
I think that a lot of it comes down to implementation and power filtering. If the designers do it right a built in streamer is great. The same is true of using a Dac as a pre-amp. I had D’Agostino momentum monos and the hd pre with an MSB discrete. I upgraded to the premier and was able to audition the MSB s202 amp in my system. I found that the amp and Dac paired together were so good that I did not hear enough of a benefit in owning the D’Agostino gear and sold it off and bought the MSB amp.