spend on the streamer or on the DAC ?

I have not listened to ethernet vs. usb myself, but I have two local dealerships that I like, and both don't like usb connection.  My own system, Naim 555 server and uniti/core ripper and storage, is ethernet connected. 

The Naim has the server and DAC in one box, but they do go to extremes when it comes to internal isolation.  First, there is a separate power supply box which has multiple power feeds coming from the box to isolate the feed to the various functions in the server/DAC.  The DAC is isolated from the rest of the server by being in a faraday cage; to enter the cage, the digital signal is converted to an optical signal.

Hello,
I have a Sonos connect as the source and an Emotiva DAC. It sounds amazing! It plays at CD quality plus the Emotiva DAC is fully balanced along with the rest of my system. Someday I hope to upgrade my DAC to what most of you have but for now I am very happy with my system. 

I recently purchased a naim 5 xs for my office system, (Focal Utopia, Flicks Euphoria, Audioquest Vodka) streamed direct from a dedicated modem. I also have a two channel system in a dedicated listening room. I have been so impressed with the naim unit, I exchanged it with my Lumin D2 on my two channel system. For my listening preferences, the naim easily outperforms the Lumin. A pretty good comparison, same system, same environment. The Lumin is very nice, but entry level, you may have a better experience with a higher end Lumin. I would also add, I prefer the naim interface. Many of the negatives you hear about the Lumin connectivity and less than ideal app. I have experienced.

I tend to go with the DAC because if you hear a composition you find so beautiful you might want to download it into your library and get it in high resolution it will sound better than what you can stream. If you run into unexpected financial ruin and you have to give up streaming subscriptions you get to keep your DAC and the rest of your system.

concur that sonos streamer, with a w4s digital reclocker upgrade (or outboard reclocker) is an excellent sounding source... delivers spdif at 96k

plus using the sonos software is easy peasy 

this and the bluesound node 2i are excellent cost effective streamers that make no apologies to more expensive ones, unless you want other forms of output like i2s...