You are most welcome Scott,
I am happy to be able to provide some insight based on my experience.
Once being fairly selfish on such finding of hidden treats in the quest for sound, and being involved in this racket for well over two decades brought me to a realization that the more, the merrier it is to share. I do enjoy sharing and learning from others now.
The NAD you have is such a great little piece of achievement by this long running company, not forgetting their newer upper M3 series as well which is a real delight.
Its really exciting when you find such equipment that is a fraction of the cost but delivers a substantial portion of the very best out there.
The Krell 400xi Integrated was a breakthrough in design in my opinion, massive Toroid, surface mount direct coupled and no caps
.its a true feast and I will continue to say Dan is the Man, the master of amplifier designs. That little integrated, 30lb with lightning speed and current, transparency and resolution and not forgetting the bottom end was just mind boggling for $2500, a true Krell signature right there. The looks is truly a bonus compared to what that amp is capable of doing.
When I first heard it, it was sad since I used to enjoy my Creek 4330mk2 in the early days until the Krell was placed into the chain and it was just annihilated it in every way (not a fair test obviously with the price ratio). It just had Gobs and gobs of power, control and detail that I was not accustomed to from the little Creek.
I had never ever heard monitors sound so big and full until I was introduced to the Krell, it was driving a pair of Sonus Faber Electas. Good memories most certainly. It never ever sounded like my bigger Krells such as the FPB600c or the Monos but it had that signature Krell sound assured with a good portion of its performance is a much lighter package. That is true engineering!
The Stello ai500 reminds me of the Krell 400xi but with much greater Neutrality which I think would entice many new listeners who are seeking for that missing edge that some amplifiers fail to deliver.
Good luck
Ravi