You need more volume out of the NFB-28?! Using the balanced output, it's capable of 8w @ 40ohms! On high gain, turning the nob to 30/80 is crazy loud for most music using the HE—560's.
Do you have an nfb-28? And if so... What revision. 2014 or 2015. I found that each version is significantly different with a completely different volume curve for each device. Stillhart has 2014 and I have 2015... When he is around 32, the db level is about the same on my unit around 58.
So depending on recording, no... My nfb-28 2015 edition is not loud enough.
Kingwa tried to explain to me why, but I didn't quite understand it well enough to repost the explanation.