This is a great thread. I've just started building a digital system and my first purchase was the Zen Stream and so far I've been really impressed. I'm feeding it with a 15v iPower X from a good Power Conditioner with a couple of AC iPurifiers plugged in.
I've been down a deep rabbit hole with Ethernet and tried all sorts of expensive components (EE 8 Switch, SotM iSO CAT 7, Audioquest, Chord and SotM cables) and not-so-expensive (Cisco 2960, SFPs, 10Gtek FMCs etc.). Try as I may I can't beat the sound from a solid Wi-Fi connection to the Zen Stream!
My current DAC is the Zen DAC v2 (I know, it's really cheap but it sounds really good to my ears!) I've tried several USB cables from Wireworld and the ifi Mercury 3. I'm now using the stock USB cable supplied with the DAC and an ifi iPurifier 3. The iPurifier 3 makes a massive difference to SQ and with it plugged in the more expensive USB cables are redundant.
With some good quality RCA cables to a Topping PA5 and some lovely speaker cables to some great Wharfedale speakers, I'm actually at a loss on what I might improve!
The DAC is an obvious area of improvement and I might audition a Zen DAC Signature v2 and a Denafrips Ares II to see if they make any audible difference.
It's reassuring to know that the Zen Stream is potentially "as good" as some of the far more expensive models as I had my eye on the Auralic Ares G1.1 but that is quite a significant cost uplift and doesn't offer MQA decoding.
If ifi can offer native Qobuz integration to the Zen Stream that would be a game changer as I really want to try Qobuz but the current need for a third-party app kills it for me.