Looking for best streamer without DAC under $3500

I honestly doubt the D2 would better your onyx/ambre combo.
Different yes
Better ? in the ears of the beholder.

I have an Aurender N100 and tbh I have just changed to using Roon, running core on my computer and using a Sonore Microrendu as a bridge then straight into my MHDT Orchid DAC and that sounds slightly better to my ears. A little more air and easier to pick out instruments, not quite as dark as the N100.

In fact I was considering buying an Onyx/Ambre combo using i2s to see what that sounds like.

The N100 does allow the use of Spotify but the sq on that is blown away by Qobuz hires imho

I'm sure it won't sound better that's how I would just use it as a streamer, but it would be fun to compare as well. I'm only considering it because it's cheaper than the mini.

The Ambre is really good, i just want spotify among other aps and yes I do use Roon. 

Well its a fair price and you may find they would go down some given the current economic crisis.
I use Spotify on my phone only to play in the car as Qobuz beats it soundly in SQ at least in my system to my ears.
That said the Spotify catalog is larger than Qobuz so there is that for sure.

Has anyone compared the Lumin U1 Mini against the Auralic Aries G1?

OP
If you really want to try the D2, take a look at this
at the asking price it is just $1575 USD.

https://www.usaudiomart.com/details/649607429-lumin-d2-silver-trade-in/