Point of diminishing returns for a Network Streamers?

I think the iFi Zen Stream offers a lot of performance/$, and it also incorporates iFi’s noise reduction technology that, especially in your case using an old computer as a source, may be particularly beneficial. If you go to Hifi Shark and search for the Zen Stream there was a guy selling new units for $325 — I just bought mine from him and transaction was great (hooking it up today and will follow up with first impressions vs. streaming Qobuz direct from my iPad/iPhone). FWIW and best of luck.

I've built mine out of a Pi / Ubuntu / Roon with a case the size of a deck of cards plus iFi low noise power supplies for the streamer and DAC.  I'd consider upgrading but I have not yet heard a reason to.

First off, a general purpose Mac or laptop is not a ideal source for streaming from Qobuz or Tidal. Couple of things when considering a streaming source,

1) Whole system holistic approach

2) How far you’re willing to go with Ethernet optimization

What DAC you’re currently using?

A good streaming system is not plug n play. There are plenty of threads here that speaks to end users positive experiences with getting the best sound out of streaming by way of employing some sort of noise filtering devices between your router and streaming box.

To answer your question, one glaring difference between Project / iFI Zen and Lumin Mini is with Project / iFI you would need a good outboard Linear Power Supply. I don’t like to clutter my space with multiple boxes (that’s just me). So if you love your current DAC then go with Lumin U1 Mini. If you subscribe to clean and fewer boxes in the signal chain approach then something like Lumin D2 or T2 would be a worthy companion to your Luxman Integrated. Another major consideration is app interface, Lumin app is very good, it certainly not as fancy and complexed as Roon but quite good enough to perform all the basic functions of searching and curating your favorite music with ease thus eliminating your dependency on Roon app and the need for separate server to run Roon Core (more boxes, filters and linear power supplies).

Will you hear a difference in SQ between Project and Lumin, I believe if you set it up correctly, your Luxman Integrated is perfectly capable of conveying the nuances between the two aforementioned streamers.

If streaming is going to be your only source, then don’t monkey around with interm solutions. A properly setup streaming system is capable of transcending both CD and Vinyl playback. I have done it (my system is listed here in virtual systems).

Once you sort out your choice of streamer, give it a go for Network Acoustics passive filters, they come with no questions asked 30 days return policy.

Enjoy the ride!