What Vinark says plus in addition: ADI-2 DAC / PRO FS make a difference in sound and for phones. Just try!

Either Solo or in combination with a RME recording interface with TotalMix FX which gives you more options for monitor mixes and routing capabilities.

Alternatively a combination of i.e. RayDAT and ADI-2 FS (without phones section), also possible.
Or RayDAT and ADI-2 Pro FS and 1-3 ADI-2 FS ...

You can combine those units as you prefer.

A friend of mine was amazed that his current inexpensive Yamaha Monitors sounded better with the ADI-2 Pro.
Now he bought Audeze LCD-3 and also considers to get better monitors, potentially the same that I use (Geithain RL906).

The ADI-2 Pro FS is IMHO a very strong basement for good sound in terms of D/A for phones and speakers.
I use it to drive my Geithains and EDIT: the smaller model (ADI-2 DAC) as D/A converter for Accuphase / B&W
monitors in the HiFi corner. And you hear the good sound and room presentation even in a not optimized room.

Considering the feature density and quality I think it's the best that you can currently get for money and the price is fair.

Just try it out, better than to talk a lot about it, you need to hear it on your own and then decide.

Careful with the amount of outputs that you see on the back.

See also handbook, Block diagrams chapter 17 and analog outputs chapter 21.

The ADI-2 Pro FS has 1 A/D and 2 D/A converter built-in and chapter 21 tells:
[...]The TS outputs, XLR outputs and the front outputs PH 1/2 are fed from the same DAC, hence carry the same signal (channels 1/2). They all have individual driver stages with different output levels, see next chapters for details.[...]

I recommend you to combine the ADI-2 Pro FS with a recording devices to have
- TotalMix FX for easier routing and
- some more analog outputs to support monitor B

If you want to have the same quality for your Monitor B and easily switchable (by TotalMix) then you could think of i.e. this combination of RME interfaces:
- RayDAT
- ADI-2 Pro FS
- ADI-2 FS (for the second pair of monitors)

ADI-2 Pro and ADI-2 FS have the same quality and can get signals from ADAT (1st two channels) and SPDIF, so the RayDAT is ideal to drive two units and optionally also offers a WC module.

The RayDAT offers 4xADAT, AES, SPDIF, 2x MIDI.

You would connect the ADI-2 Pro FS via AES and select on the unit between Main out and Phones.
If you want to control this fully via TotalMix FX it's also possible by using SPDIF and AES, you can configure then the ADI-2 Pro to route AES to Main Monitors and SPDIF to phones.

And then you have still some ADAT channels free to connect 3 or 4 ADI-2 FS to get the same quality AD/DA conversion like with the ADI-2 Pro FS.

Potentially it's also sufficient for you to have only the main monitors connected to ADI-2 Pro FS grade of D/A conversion.

Then you could leave out additional ADI-2 FS and concentrate on getting i.e. a combination of  UFX II and ADI-2 Pro FS.
Then you have with the UFX II: DURec, Autoset, very nice analog section, with very nice Mic preamps (75dB gain range).

See also
https://www.tonstudio-forum.de/blog/ind … 8-RME-UFX/
https://www.tonstudio-forum.de/blog/ind … ort-DE-EN/
https://www.tonstudio-forum.de/blog/ind … our-Setup/

You can use the ADI-2 Pro as main audio interface, but then you do not have TotalMix FX
and need to fully rely on the predefined signal flows provided by the modes which you can see in the block diagrams.

If you are mixing and mastering you usually want to have more flexibility in terms of routing and direct monitoring.

The ADI-2 Pro was never designed as recording interface, more as coverter, phones preamp, etc .. a very flexible unit.
But for recording I would only use it in combination with a recording interface offering the flexibility and comfort of TotalMix FX.

UFX II and ADI-2 Pro FS will be a very nice combination, maybe consider an ARC USB as well.