I bought Dave_b's 400xi and I also have listened to the
S300I at a local dealer. While I agree the S300I is more
articulate it is also a bit colder sounding. Bass on
the S300I is tighter too but I prefer the 400xi's slightly
looser bass as I think it allows the speakers to "let go"
a bit more.
The S300I has much better aesthetics and a far nicer
remote as well but for now I prefer the warmer sound of
the 400xi. In fact this is the warmest Integrated Amp
I have owned. Much warmer than the Classe' Audio separates
that I used to own. I can definitely see how people
would prefer the S300I over the 400xi. It's more refined
from top to bottom. It really depends on your preferences.
For me and my tastes, I prefer the 400xi.