Best DAC to go with Aurender N100H?

nekoaudio, there is no comparison between the older Lumin A1 or T1 vs the new T2 platform. 

On paper the T1 or A1 with the Lundhal transformers and outboard linear power supply should sound better, but that would be suicide for a manufactuer to make a new product which isn't better than the older series.

So the T2 with the dual Ess chips still handily outperforms the older units sonically run the T2 as a DSD upconverter and the sound is a bit lusher and the T2 just sounds amazing. Huge 3d soundstage, great resolution and it is still very musical.

The bingster, the built in Hegel dacs are good but do have a sound which is clean with good details, but the built in dac would be equvilent to probably a $1,200-2,000 externral dac from Hegel.

The Aqua Hifi Dacs are much more liquid sounding, so it is not surprising that you found a $4k outboard dac that would sound better. 

The Aqua Hifi La Voice MK III is even better than your older MK II the nice thing with Aqua is you can upgrade your older model into the current one pretty easily as you have found out, give the MK III upgrades a few hundred hours and you will see the improvements in the MK III they actually replace quite a number of boads so the break in is substantial. 

Dave and Troy
Audio Doctor NJ Lumin and Aqua Dealers

I do have a bias towards NOS DACs.
As I research this further, I come to find out that Metrum makes a streamer called the Ambre.
Has anybody out there heard the Ambre+Onyx combo??

Primaluna’s new DAC offering “sounds” like it may be right up your alley. 

I also run my Aurender (ACS10) thru an EEM DAC2 and it delivers all I could ask in terms of sound; it is the combination I was looking for.  The Aurender Conductor software provides flexibility  and the built-in TEAC drive for ripping is convenient and provides plenty of hard drive storage.

I recommend you consider the Ayre CODEX DAC.  It is excellent and its cost is $1,999.   Please see:

https://www.ayre.com/products/digital/codex/

It operates as a DAC or a Preamp/DAC.   It only has a USB and Toslink inputs.  I strongly recommend you use its balanced XLR cables to your amplifier.  It sounds much better when used with its balanced XLR connections.   

Another option might be the Schiit YGGY DAC.   I hope you are streaming Qobuz hi-res on your Aurender N100H.  Their 24-bit/96 and 24-bit/192 albums are terrific sounding.   Enjoy.