In general:
Have a look at ADI-2/4 Pro SE.
For your purpose it has some advantages regarding analog routing.
Specifically that rear TRSs out can be independently feed by DA-channel 3/4, while XLRs out can be from DA-channel 1/2.

Yes.

Yes.

Yes.

The limitation is, you have two stereo DA-channels.
So, while running an analog mastering chain you CAN monitor through both speakers AND headphones, but not with independent sound and volume control.

As monitoring through both at the same time doesn’t make too much sense, the various switching options between front and rear (e.g. push the Volume dial for 1/2 second) should suffice for the job.

Yes on ADI-2 Pro – no on ADI-2/4 Pro SE.
On ADI-2 Pro the front TRS PH 3/4 typically would be used to drive the mastering chain.
Albeit it’s a dedicated ‘phones out, audio quality is exactly the same like the rear line outs.
With proper cable even an impedance balanced send is possible, if needed.

For extensive studio work a recording interface always is a good idea, at least if you intend to do stuff beyond mastering.

The built-in headphone amp in the UFX series is more than sufficient to drive most headphones to ear-bleeding levels.
No need for extra hustle with extra boxes.
What ‘phones do you use?

The converter quality is beyond good and bad in any case.

On the other hand, as mentioned above, ADI-2 Pro in fact IS suited as central unit for in-the-box producing, vocal- and instrument-overdub and analog mastering.
Just the connection is little unconventional, but without audio compromise.

Hi Bjørn,

I think the best flexibility you get by combining an RME recording interface with TotalMix FX
and then additionally ADI-2 Pro FS or ADI-2/4 Pro SE.

You can integrate them easily into your setup as shown in this blog article:
https://www.tonstudio-forum.de/blog/Ent … our-Setup/

The Apollo Twin X you can't use for this purpose because it is missing an ADAT output
It's somehow a shame that Apollo didn't provide a pair of ADAT I/O for in and out in this price range.

It would be better anyway to use an RME recording interface because TotalMix FX gives you the best comfort and flexibility when it comes to monitor mixes, routing and additional nice features.

Additionally you get RoomEQ with recording interfaces like UCX II, UFX II (and or course UFX III).

The combination of UFX II and ADI-2 Pro FS R BE would be ideal because it gives you many options in terms of I/O (price around €3798).

A less expensive alternative would be to use the UCX II and ADI-2 Pro FS R BE instead (price around € 3028).

Both interfaces UFX II and UCX II offer an AES port, which also provides galvanic isolation. Especially important on the UCX II with only 1x ADAT I/O to keep that port free for any potential future expansions.
If you do not need ADAT for other purposes then connect the reference converter via ADAT, otherwise you need to use the breakout cable for AES. So, using ADAT is one cable less.

A safer investment is the UFX II with AES and 2x ADAT I/O because then you can even connect two 8-port devices or one at double speed if you should decide to work in double speed.

Just as an information: the UFX II (and UFX III with MADI) have the same converter as the former reference converter ADI-2 Pro FS.

So, if you do not necessarily want or need the advantages and special features of the ADI-2 Pro FS or ADI-2/4 Pro SE, then you could also start with UFX II or even UFX III which gives you even more flexibility by MADI to connect even more devices if you think that could be needed in the long run.

Only to put one example, why UFX III with MADI might be useful.
If you should be interested connecting smth like a 12Mic or M-1620 Pro in the future, then
a) 1 ADAT port of UCX II would be too few
b) remote control via Auxdevice is only possible via MIDI over MADI as the 12Mic has no MIDI ports, but you could use RME connector via LAN
c) if you should intend to work at double speed, then even 2x ADAT I/O would only be sufficient for connecting devices with 8 ports, but not 12mic or M-1620 Pro.

If you can exclude to expand the setup, or in other words, if the primary use to work "itb" then you do not need UFX III and MADI.