Best Server To Run Roon Core

best input by far is ethernet.

you can see my system on Audiogon.

@newtoncr -- it was actually I who asked about the differences between Lumin U1 and Wolf Audio. Thank you for the detailed comparison. Very helpful, and sounds like you’re thrilled with the server. I was seriously considering Lumin U1 at one point but will definitely do some due diligence on Wolf Audio before making the final decision. Another product that I’ve great things about is Aurender N10/20, but I’m too committed to Roon at this point.

You can run a music server on any computer you want to start and sample the waters. 
You might find that to be just fine.

I never recommend going for “the best” right out of the gate.  The best may just appear to be best based on cost.   
Walk before you run. 
Also for cd res  streaming I’d recommend a wireless connection from server to streamer to help keep the gear that makes music isolated from what is typically a noisy wired computer network.  Others swear by using a wired network connection for the streamer.  Both done right will likely be just fine.  

BACCH-SP appears to have preamp and dac capability as well. It is intriguing but I would be interested in how well it does all the things that it is designed to do

The main thing BACCH is designed to do is crosstalk cancellation for "3D" effects on soundstage and imaging. For that, you don’t need to spend $20K+ on a BACCH-SP device. You can get the BACCH4Mac version ($980-$6980). Theoretica offers a pre-configured Mac Mini, which you also can use to run Roon Core.

@mapman  " Walk before you run"  . Good words to live by! Excellent advice.