Probably best covered in its own thread - there is one here
…but in summary, some prefer the sound (sweeter - not as heavy - fast - more classic “Naim” (whatever that is to people’s ears)) and when you combine that with an amp that is half the price and 30% smaller…it ticks a lot of people’s boxes more than the 500.
I have the 500 - but had the 300 - the 500 does give more “HiFi” - so more bass, more air, more headroom, bigger soundstage (you know…all those awful Hi-Fi terms
) but it does possibly lose a bit of speed and sweetness in doing so. Do I think the 500 is better? …for me, yes…but I can understand those that don’t.