I have a couple of Nc400 monoblocks coming next week and I have never really thought about this gain-stuff. For the time being I will be driving them with Minidsp 4x10hd using balanced output. According to the manual, I have a choice between 4v output voltage and 8v through a dipswitch on the board. How does this stuff work, what should I pick?
Go for 4 V, and even that is 6 dB too high for 400 W full output into 4 Ω, so make sure you don't turn up gain too much on the minidsp.