I don't have one. It belongs to a friend. Yes it's about sound quality, but that can come through sensible design as well as the lash up that is the NVA. (Personally, I don't think it gets close to my Alpha 9 as far as sound quality)
The NVA is badly designed IMO. There is no HF stability, it is not properly stable with any speaker cable, not just specific capacitive values, therefore there is always the chance of a 'fry up' for want of a better word. Just touching the speaker cables could be enough to induce sufficient RF current to cause it to oscillate, and as there is no protection either (more 'bad for sound quality' nonsense) there is always the chance that it could take out your speakers before it cooks itself.
Personally, I wouldn't own one - and I do understand this stuff on a technical level, rather than just being blessed with golden ears (if such a thing is any more than plain old hifi 'expert' twaddle)
I don't believe good feedback (no pun intended) on eBay is necessarily an indication of a great product either. As I said earlier, serious hifi folk can be as gullible as hell!
But then, you pays your money...
"Two very small men cutting steps in the roof of the world"