Hello left turn_
According to the data sheet, an impedance of up to 430 ohms is specified for the monitor output. However, I have not tested this myself.
https://focusrite.com/de...

I hope this helps you.

I use the 250 version with the 3rd Gen focusrite solo. You can adjust the volume within the DAW. But then you definitely have to rely on the theory when saving. As far as I know, the solo has an output of around 180-200 ohms for headphones. As far as I know, it only goes up to 300 from 2i2 onwards. But I got the solo for the beginning anyway and the plugins are really great for the beginning, no matter what genre. Outside of the DAW, you have to hit MAX vol otherwise the music won't always come across as loud.

All in all, however, definitely good to use. The dt 770 are also absolutely great headphones. And if I still feel like it, I'll upgrade the interface anyway. But for anything under 200-300euros you can't go past focusrite.

Long story short. The 250 work. Full volume with the 80, but in the long run it's better to take the 250 and either downgrade it at some point or put a decent reciever on it, then you'll just have the interface exclusively as a sound card.