I also had (have) a 356BEE, and replaced it with one Vidar and Freya +. I'm selling the NAD. In my case, I had no noise from the Vidars coming through the speakers, but a very slight hum when I put my ear within an inch or two of the amp. I swapped the NAD and Freya/Vidar back and forth a few times on various tracks guided by notes taken while listening to the NAD - drum at x timestamp, cymbals at another timestamp, etc., and the Vidar made enough difference to earn its keep.
Imaging was also much better with the Vidar, with sounds seeming to emanate from above the speaker at times, not from the speaker. That really got my attention. I wondered if the preamp was the difference so I powered the Vidar from NAD pre out and difference was same. I replaced NAD with a B&K preamp and no change. Freya tubes also took some of the 'ice pick' sharpness out of higher treble which was definitely appreciated.
I cannot explain any of this. All I know is that I spent a week going back and forth scribbling annotations to my track notes and I could not blame perceived difference on panacea. I did not want the Schiit product so much as wanting to see what could better the NAD. I was prepared to buy a used NAD C375BEE and save a few hundred dollars, but what I heard from the 356 told me I'd get more watts and not much else with the 375.
Speakers are Focal Aria 926, known to be a bit bright. Freya smoothed that out, but bass control was in a different league, and that's the Vidar's doing.