Wyred 4 Sound vs. Roon Nucleus

You might also look at smallgreencomputer,com , they are very helpful and sell a kit with a roon server, endpoint, and optional upgraded power supply. Also lots of good information on how to set it up

The Roon Nucleus is a piece of hardware that Roon developed to specifically run their program.  I tried my Roon trial on an aging MacAir and the computer severely overheated when it got hung up trying to run the program so I can appreciate where a dedicated piece of hardware makes sense.  Otoh Roon is primarily a software company that doesn’t have a history designing audio components, unlike W4S.
  I’m not an IT guy but Roon is a large program that needs some computer firepower to work best  (I am basing this opinion on my limited trial and on the experiences that I have encountered here).  I think the one critical spec might be the RAM.  Roon specifies a minimum RAM and imo I would make sure the W4S at least doubles it.  Otherwise, if running Roon is the priority, and the choices are limited to the two that you have specified, I would go for the Nucleus

+1 on the Small Green Computer. Mine has only hung up a couple times. Generally very solid. Will run other media software programs as well.

Can the W4S DAC2v2SE act as a ROON endpoint? If not you gonna need one.
https://www.youtube.com/watch?v=I2WxKDAoVsA

If sound quality is your primary consideration, Roon may not be your best choice. By all accounts, Roon is wonderful for music file management, but other server/streamer setups using leaner (and quieter) software may sound better. Check out the A-gon thread by Grannyring describing the sound comparisons between Roon and the new software that runs on Innuos hardware. You may still decide that Roon's user interface is worth making some compromises in sound quality, but at least you'll be making decisions with eyes (and ears) wide open.

If sound quality is your primary consideration, Roon may not be your best choice.

Which brings up another question, what is your music source? Ripped files,music service , both?

Thinking of using Qobuz and/or Tidal as the primary source. 

There is a Bryston BDP pi over on USAudiomart with a LPS for ~$750. The interface is Manic Moose and the player is open source MPD. I think it sounds a bit better than Roon and it has native access to Tidal and Qobuz. The units are discontinued now but Bryston still provides support. MM will not be near the elegant interface of Roon but its a lot cheaper option. It will also function as Roon endpoint if you decide to invest in the Roon immersive interface and infrastructure. The BDP pi is a lot of bang for the buck in SQ. Needs a hard wired network connection and has USB,optical and Coax out.

I purchased a used Antipodes Core to run Roon and it was an improvement as it is purpose built for that task.  But I don't use it for Roon anymore it just a NAS now.

I have an Innuos server and Roon was better on the Innuos than the Antipodes when experimental mode was used.  Experimental mode lowered the noise floor and I was able to hear how much of a negative effect the DSP in Roon added.  Without experimental mode I thought the DSP helped but now I feel it was just masking some of the grunge.

Now with the new free Innuos Sense app while it may not be as functional as Roon  it is very easy to hear the the grunge Roon adds to the sound.  I was fortunate Sense came out just as my Roon membership came due.  

If your looking for a better sound start with an Innuos server and get the free Sense app.  It integrates with Tidal and Qobuz and they will definitely sound better with Sense than Roon.

However,  if you rip a CD in wav on the Innuos server and compare it to a hi-rez file on Tidal or Qobuz you might be dissappointed in Tidal and Qobuz.