I will provide my perspective as I am a big proponent of the Naits.
I own a Nait 2, Nait 3R (split), and a Supernait 2. In the past, have owned a Nait 5, 5i, and XS. All I can say is that they all sound wonderful. I would like to try a 5i again…seem to remember that one having an interesting personality and it was my gateway. Liked the Nait 5 the least.
Nait 2 has a special magic, density, and ease to the sound (“ultimate” restored by AV Options). The ease and flow is something hard to convey and antithetical to the limited power this device has. The phono stage is also quite good. My external phono is superior but would not miss it.
Speakers are Fink Team Kim and sometimes Quads. Even though the Fink Team Kims are 86db sensitive, they are fairly easy to drive and have a damping switch on the rear and the middle option matches perfectly with Naim (!). Also helps that my room is 5.2m X 3.7m and I sit 2.5 meters from the speakers and loudest listening is peaks in the high 80s/low 90s decibels. Like the Quads, the Kims are a lifetime speaker for me.
People talk about what amps can drive what speakers and rarely mention the above factors with any sort of precision, which are incredibly important. I am sure you know this.
The other factor is Naim amps always provide a nice amount of current (one reason why the Nait 2 is always recommended with Quad ESL). Thusly, in the right setting, can drive all kinds of speakers. I am highly confident the Nait 50 will be terrific given the amount of current and placed in the right situation. Certain aspects like the increased power, the volume control, and the switching are in the Nait 50s favor. Also attractive is the effort to model, at least partially, the phono stage on the Nait 1.
Under these conditions, any of these lower powered Naim amplifiers become quite competitive. I do have much more powerful amplifiers that are occasionally used yet can also admit that aesthetically, I like smaller and less boxes appeals to me. So if looking for bias, that would be one of them. However, it’s quite simple: although they theoretically offer more, I don’t listen to those devices as often as they don’t have the Naim character.
May not answer your question but the best I can do!