Best streamers WITHOUT a DAC

You haven’t specified a budget but the Antipodes K50 would meet all your needs and deliver reference level performance.  It is $15k but one of the great servers in the world.  
 

A hybrid, 2 Box approach could be interesting.  Something like an Antipodes S40 with a Bricasti M5 would be half the price and is a pretty incredible solution.  $7400 combined and again, would do everything you are asking for.  
 

the Lumin U1 is a little older at this point but still offers great support for current platforms.  It is a streamer only at $6k

the U1 Mini is a smaller, more streamlined version at $2100.  All of these are a step up from a Node.

I am an Antipodes and Bricasti dealer.  I am considering Lumin at this time but am not a retailer at this time. 
 

I can highly recommend the iFi Zen Stream. Has S/PDIF out.

Aurender N-100C has a S/PIDF connection,  I use the USB version and enjoy it. Good luck with search. 

@verdantaudio wouldn't the OP just need the Bricasti M5 for what he is asking about? Why the Antipodes S40? Just curious.

@rsf507 i will use Roon as an example because it is so common.  The Bricasti M5 is a Roon Endpoint but does not run Roon Server.  You can run room server on a ton of devices but a PC or Mac Mini can perform poorly and mitigate the benefit you are getting from the Bricasti.  Mac Mini’s in particular are awful IMO and any dedicated server; small green, Roon Nucleus, etc… will outperform it.  
 

the OP mentions they are looking for flexibility and reference quality which is why I suggested Anyipodes.  For Roon in particular, an M5 and a Roon Nucleus.  

to run Roon with Lumin you would need a separate server as well but since it has its own streaming software option, you can avoid the separate server.  Not my preference but it is an option as I personally see a lot of value in a service based on my experience.