I've heard a lot of people complain about the noise on the minidsp units. I have used both the 2x4 and the 2x4hd, both are so quiet my 110db/W horns are virtually silent. No hiss until my ear almost touches the horn.
This is the case if your gain structure is good, which is not what many people manage to achieve.
This is true...most probably don't give it a second thought. My amps are all low gain for this purpose.
Yep. The amp that drives my 100dB/W/M horns has a voltage gain of five (14dB). My system is noise free, even at very close range, and uses MiniDSP 2x4HD.
I've not had noise problems with MiniDSP 2x4 or 2x4 HD either, and I use amps with the usual ~26dB of gain. Speakers are in the 90-98dB sensitivity range.