Looking up the specs on the NAD shows 39dB gain compared to the Saga+Vidar total of 27. The tube stage on the Freya+ is 12dB so that should put you back to about the same level.
The way I understand it is the gain is an increase in voltage but in order to not distort there needs to be enough available current to support the signal accurately. So a 400W amp with 24dB of gain won’t sound as loud as a 100W amp with 30dB of gain. Sometimes the distortion is what makes it feel loud though. I remember cranking up my first big clean amp and having no clue how loud it actually was compared to the consumer receiver it replaced until I didn’t hear the phone ring.
The way I understand it is the gain is an increase in voltage but in order to not distort there needs to be enough available current to support the signal accurately. So a 400W amp with 24dB of gain won’t sound as loud as a 100W amp with 30dB of gain. Sometimes the distortion is what makes it feel loud though. I remember cranking up my first big clean amp and having no clue how loud it actually was compared to the consumer receiver it replaced until I didn’t hear the phone ring.