Neumann KH 120 A
Neumann KH 80 DSP A
Option after winning the lottery: KH 750 DSP (automatic room modem reduction at the listening position)
But:
Optimal listening with two people is not possible!
By listening with headphones, you are used to direct sound:
Visit a person with a speaker stereo-system in a living room. Sit in the listening position and listen to an audio source. After some time, hold both hands behind your ear and turn your hands until you get the highest volume for high frequencies, ...
In order not to be disappointed, these are the main parameters to consider before looking at where you could borrow speakers for testing:
1. Room: size: area, height (room modes) / material: walls, ceiling, floor (reverberation time)
2. Position of the speakers in the room
3. Listening position to (2)
4. Which lower frequency would you like to hear (at the listening position)?
5. Cables
6. Literature
To 1:
Determine the room modes (standing waves) and the reverberation time. From a technical aspect, influencing the room modes and reverberation time would be optimally possible via passive elements. An electronic influence of the room modes - e.g. via PEQ (ADI-2 DAC has only 5 x peak, the frequency range is limited) - is a compromise solution: e.g. a correction would only be possible for a certain listening position and also only for one person! The impulse behaviour deteriorates.
Calculation of the room modes:
e.g.:
http://www.sengpielaudio.com/calculator-roommodes.htm
https://amcoustics.com/tools/amroc
...
To 2. and 3.:
Determines the frequencies that are cancelled out or changed in amplitude by reflections from the walls (also ceiling, floor).
To 3.:
Determines the max. required undistorted output (SPL) of the speakers.
The greater the distance between the listening position and the speakers, the less precise the sound.
Optimal listening with two people is not possible! But if the distance is big enough, you both have about the same bad sound and you don't need very good active monitors.
To 4:
The lower this frequency should be, the more difficult and expensive your "loudspeaker project" will be.
Re 5:
Standard microphone cables are sufficient - anything else is wasted money!
Re 6:
https://en-de.neumann.com/
Setting up Studio Monitors Guide (English)
https://en-de.neumann.com/product_files/7670/download
...
https://www.genelec.com
https://www.genelec.com/correct-monitors
https://www.genelec.com/monitor-placement
...