Zeos has a review on youtube of the Buchardt S400. According to him they aren’t really appropriate for nearfield, too diffuse sounding and preferred coaxial Kef R3.
Which reminds me of my experiment with using Revel M126BE and Revel Gem2s nearfield. Neither worked well. I believe speakers using large waveguide designs measure well in the midfield (2 meters or so) in terms of dispersion and look competitive with a coaxial design there but not once you move into the nearfield since they aren’t a true point source like a coaxial--a lot of the output you are getting is from reflections (direct output of the tweeter reflecting off the waveguide) which gives an excessively diffuse sound nearfield resulting in poor imaging.
This doesn’t matter in the mid-field because by the time you are out of the nearfield the majority of the sound you hear is reflections anyway, so I believe there’s sort of a minimum useful distance for large tweeter waveguide designs of at least several feet.
To me the ultimate nearfield monitor is a 3-way coaxial. Obviously if you aren’t budget limited, Kef Reference 1, Genelec 8331/41/51 or TAD ME-1 would be my first picks. But on a budget Kef R3 (or older R300) is probably the best. A 2-way coaxial isn’t quite as good because midrange excursion causes some doppler shift which affects the frequency response--unless you are listening at low SPLs (< 75).