@waedi: its not about the loudness of music.

BTW: ADI-2 and ADI-2 FS are different products with a much different feature set.
So I would use the real names of the reference converters to not get confused about what product you mean.
In the context it was clear, but 1st it also irritated me what you mean.

AFAIK Dynamic loudness you only get with the reference converters.

I didn't hear about any VST plugin doing the same thing.
If you ask ChatGPT (I hate the bad quality of the tool, but to get at least an idea) you get a list of plugins.
But if you look at the description, it doesn't appear to do the same or in the same (easy) way as the RME dyn. loudness.

However take a look at your own, here is the list, but I have doubts that it will do the trick.
Sonimus - SonEQ Pro, Voxengo - Soniformer, FabFilter Pro-Q 3, TBProAudio - dEQ6, Hornet Plugins - Hornet VU Meter MK4.

Thanks, for the suggestions. The plugins do not offer a dynamic EQ. I currently use Equalizer APO with a loudness plugin, but was looking for alternatives, because using EQ APO sometimes has downsides. The ADI-2 DAC FS and ADI-2 Pro FS R Black Edition would fit my needs, but are quite expensive just for the loudness function. If they would allow me to make a room correction with 9 or 10 band EQ that would make the purchase interesting and cover all my listening needs. Then in combination with the Babyface used for recordings could make my package complete. If the UCX II would offer the loudness option that would also be an option for me, but currently I do not seem to find an RME product which covers all my wishes/ needs. :-(

Edit: It seems that regarding loudness and EQ both ADI-2 Pro FS R Black Edition and ADI-2 DAC FS are similar and both have basically 7 bands, when one includes the Bass and Treble control. That makes me think again if the ADI-2 DAC FS could be a solution for me already.

They do not differ in that regards.

The differences of the units you can find here on forum: https://forum.rme-audio.de/viewtopic.php?id=32506
and here in my blog article: https://www.tonstudio-forum.de/blog/Ent … ses-EN-DE/

If I were you I would get the ADI-2 Pro FS R BE.
Last recently the ADI-2 DAC FS increased in price, from under €1000 to €1200.
The difference in price between those to products was never so low like now €1699 - €1199 = €500.
In former time it was more like €1650-€990=€660.

The ADI-2 Pro FS R BE has more features and is less expensive compared to a ADI-2 DAC FS plus ADI-2 FS (to get also analog in). And still such an "enhancement" with ADI-2 FS would not deliver you the same features compared buying an ADI-2 Pro FS directly upfront.

Two DAC chips instead of one
digital outputs
additional AES I/O
two of the same headphone outputs
reference levels more according to studio than HiFi use
analog inputs
Sample Rate Converter (SRC) just in case you want to connect a device with a fix clock or which can't become clock slave
routing options on the device itself
support for balanced phones

Simply open your mind what is more useful for you on the long run and for "only" €500 more.