Leonel, yes, that was very helpful, thank you!! It's good to know that the RCA inputs aren't compromised, as that is one of the things that could rule the NFB-6 out for me. Also, thanks for the clarification on the warmth vs smoothness changes Kingwa made-- I'll have to debate if that's what I want or not. (I have a particularly smooth DAC right now, and while it admittedly does sound great, it softens up a lot of my more aggressive music too much for my tastes).
And you know, everyone seems to be quite impressed with the preamp capabilities, which actually makes me a bit sad that I'll almost certainly never use them. But hey, it's nice to have nonetheless! ;)
Again, thank you very much for your impressions and assistance, Leonel!! You may have just tipped the scales on this one