Streamer's without built in DAC options?

Innuos ZenithMk3 and you can get rid of the Nucleus. 

Lumin U1 -- http://www.luminmusic.com/lumin-u1.html

Wolf Audio - Luna or Luna “R”

https://wolfaudiosystems.com/product/the-luna/

Check out various options from Aurender and you can get rid of Nucleus.  The conductor app offered by Aurender is the best app outside Roon. 

https://aurender.com

What type of streamer do want that works with the Nucleus? The Nucleus is a streamer... what are hoping to accomplish?  The term "streamer" means different things to different people and the capabilities of various streamers varies widely. For instance ......

What type of outputs do you need, just ethernet, spdif, usb or ???
Do you need internal storage, need to attach USB drives, just access NAS?
Does it need to be a Roon core like the Nucleus or will you use the Nucleus for that?

I see your DAC has a full complement of inputs, how do you want to feed it? As a Roon endpoint using ethernet or use the USB or one of the other digital inputs. 

Your question is too vague to answer properly.