What determines a streamers sound quality.

I want to purchase a streamer. I have a $4000.00
Audio Note DAC that I want to run it through. So I see no reason to purchase one that has an onboard DAC. 

Other than a streamers DAC what determines the quality of the sound. I am not getting it. How do DACless streamers differ from one another? I have been searching but have not found the answer to this particular question.  A have mosty found questions and answers to recommended streamers.

Thanks for any help