Ive own a great number of naim products and the supernait and classic series boxes are where things start to get interesting in the naim line up.
With Naim the biggest differences are actually the most trivial on paper and easily glossed over.
You say" despite the obvious being power" (paraphrasing) in naim land that's what you're paying for, and they kind of just brush past it very quickly.
Take the hood off and it's very apparent what you paying for, everything has been supercharged, everything from the volume pot (look at the size of it) to how the wire is connected and raised off the board. and board isolation.
The capabilities of the supernait are its ability to grip and not lose control allowing it to drive bigger speakers watts don't mean anything in naim land. Its all about current, they give you the VA outputs of the transformers for example. I mean look at the size difference of them.
The preamp section is of far greater quality arguably the most important part.
it's very very close to 202 and nap 200dr without hicaps/power supplies, but the supernait will surpass them with a separate power supply box, but they're lots of money but worthing thinking about
with easy to drive speakers tbh the difference aren't all that pronounced at all and very hard to hear but turn the wick up and/or give them difficult to drive speakers with large dips in the impedance and the difference if very obvious.
If it were me i'd find a second hand supernait and enjoy and add a power supply later down the road
Images attached (right image being the super nait)