Streaming Transport without DAC- few choices


I already have a very good DAC. I already have a very good preamp. There seems to be a dearth of streaming transports under $2000 which noes not include a DAC, does not include preamp function or does not include both. 
So tempted to just get a Mac mini and use that as a dedicated transport/server, played through audirvana 


128x128zavato
There are at least about 2 dozen I know of so your premise is false and under researched.
$200 of RasPi will blow away a Mac.
Sonore opticalRendu or ultraRendu

Lumin U1 Mini — most dealers will discount and bring it under 2k


iFi just released their new ZEN Stream which looks nicely done for $399 .. WiFi & ethernet connections, USB & SPDIF out, and sans DAC to name a few features.

https://ifi-audio.com/products/zen-stream/
If you're interested in Roon, they have a Nucleus which hosts their software and acts as a streamer for $1500.