Where to invest the most in the "digital chain"?

In the interests of transparency I've spent the last several hours listening to a number of pieces of music that have passages of silence as well as single instruments and acoustic vocal tracks - with these on repeat I've slowly removed a number of components from the "digital path".

The end state I have landed on is that the Wi-Fi circuit in the Zen Stream is more than good enough for a low noise signal (hence removing the Cisco 2960, EE 8Switch and SotM iSO CAT7 and assorted high-end Ethernet cables).

The connection between the Zen Stream and the Zen DAC v2 is now just the supplied USB cable and an ifi iPurifer 3.

Removing the iPurifier and re-adding it yielded the most noticeable improvement in SQ with audible noise on an MQA Studio recording of Adagio for Strings without the USB filter, and near-perfect silence with it added in.

It is worth noting that I have recently upgraded my Wi-Fi router to an ultra-powerful TP-Link DECO XC80-5g which reaches every corner of my three-story house with rock-solid high-speed connectivity.

I have my eye on several potential upgrades to the Streamer and DAC in the near future, with a preference for a Streamer that supports Qobuz natively as well as Tidal with MQA decoding.

I appreciate all the responses, even the hostile ones as they are always a test of ones self restraint ;)

I have no filters or anything special "cleaning " the ethernet.   Just the N200 connected via SPDIF so yes, the streamer is the clock.    

The N200 with my DAC sounds great,  it's much better than the Vault.  Like I said before,  demo a really good streamer and it's unlikely you'll want to take it out.

I purchased DB Audio modified Mac mini and his DAC with all options. I also have an Audio Research CD player. The Audio Research and the DB Audio system are close but my preference goes to the Mac mini + DAC. I have used a streamer linked to the inboard DAC in my Classe pre amp and its not even close. 

My opinion is much like the rest of this stuff, don't use any weak link. There is no substitute for top quality across the entire chain.

@slbjbb now that is super interesting, thanks for the insight!

@jabbaman : for what its worth, my DB Audio digital front end has a Morrow audio level 6 digital cable as well as a level 6 power cord the DAC. The Mac mini is off grid powered by a 12 volt car battery. https://www.audiocircle.com/index.php?topic=158212.0

Each step was a clear, audible improvement in detail, focus and soundstage.