Music Streamer Quality

I have a Moon 780D and I get better sound using the internal MiND streamer vs using my Meridian Sooloos MS600 to feed it via an MIT Oracle digital coax.  Not sure if this is due to a shorter signal path or just differences in the sonics of the streaming devices. 

Falconquest - There is no reason to upgrade your dac at this time... the Sonos is the weaker part of your system.  If you want to keep the Sonos, an external re-clocker or Wyred4Sound modification will make a big difference, especially if used with a good power cord.  I owned the unmodified and W4S modded Sonos with Furutech FP-320ag power cord that has the C8 connector, and this source sounded much better than the standard Sonos.  However, you can improved the sound quality even further  by moving to a small streaming source like the MicroRendu from Sonore or the SMS-200 from SOTM audio.  
 
I've owned the MicroRendu since fall 2016 and can safely say it is a major upgrade over the modified Sonos.  If the other parts of your system are reasonably good quality, you will hear music like never before.   Plus, you can use Roon to stream from Tidal, which is opens doors to other musical worlds.   BTW, I've used several dacs with the W4S Sonos in the past 3 years (Rega, Naim, PS Audio DS Junior, and Resonessence Mirus) but never really found them to transform my system like the MicroRendu with a good linear power supply (Uptone Audio LPS-1.  So does the streaming source make a difference... absolutely yes!   

Thank you kendrick,
I had pretty much decided on the W4S Sonos upgrade until your comments so I will do some more research. I do use a ifi SPDIF iPurifier between the Sonos and the dac but have not switched out the power cord. The entire front end of my system is powered through a BPT balanced power unit.

I am still researching dacs and have somewhat narrowed it down to the Holo Audio level 3 Spring dac, the Soekris dac 1541 or the Denafrips Ares. The R2R design intrigues me.

You are welcome. The IFI SPDIF iPurifier re-clocks and regenerates the signal before being processed by your dac, so I would think the benefits from a W4S upgrade would be marginal and probably not be satisfying in the long term as a primary music source. Looking back on my experience, the W4S Sonos is a very good source for the money but I wanted better sound than it could deliver. Better signal cables and better dacs helped but it always sounded like a digital source, which of course it is. That changed with the mR, which sounds similar to analog sound in my system... when using the Uptone Audio LPS.   BTW, I sold the Sonos here on AG last week; it was snapped up in one hour!

I also have an interest in R2R dacs, including some you mentioned and Metrum products. I previously mentioned trying a number of expensive dacs and not finding a meaningful, longterm improvement until replacing the Sonos with a better quality music streamer like the mR. So my caution would be don’t expect a dac to "fix" problems that are better corrected up stream, so to speak.

Another lesson recently learned, and much to my surprise, was that good quality power strips can make a difference when used with routers, modems, switches and servers. I have an Audience AR6 PDC for my stereo setup, and it helps a lot.  I recently bought a used IsoTek EVO3 Sirius for the computer gear and WOW, the improvement is amazing. All the digital grunge that accompanied the music signal is gone! Furman Audio makes some less expensive devices you could trial on home demo for around $180.  The AudioStream author uses these on his system.  

Any sense of how the MicroRendu compares to the Auralic Aries Mini? The latter seems to be quite highly regarded also. I get what you're saying about the upstream component so I will focus on that for now. One thing I have to say for Sonos is the interface is incredibly simple and stable. As for power issues, I don't worry about power with the BPT in the system.