I am floored at the length of this thread! This says a lot about Naks in general...although I haven't used mine in years, I still remember vividly the differences in the top end Naks and the others, along with other manufacturers' machines. Although I liked other decks, from various manufacturers such as Teac, Tandberg, etc., and despite having owned several other decks, I ended up with only Naks. They just sounded better to me. After selling off everything but my last two, a Dragon and a 700ZXL, I did some A-B testing.
(I had two 700ZXLs but sold one to a friend - talk about seller's remorse...)
Bottom line: to my ears, the Dragon was a superb deck, that reproduced music from top to bottom beautifully.
HOWEVER, again, to my ears, the 700ZXL had a more 'organic', smoother sound...and could reproduce bass notes that you couldn't even hear. I believe they tested down to some absurd frequency, like 11 Hz. You need a good subwoofer to really hear, and feel, what they can do.
One other thing to note: the 700ZXL was designed and built with a cost-no-object philosophy that seemed to end with the death of Etsuro Nakamichi. The amount of shielding and dampening material used, and the silence of the mechanism itself, were beyond reproach - and I am certain that it added to the quality of the reproduced sound.
When playing tapes from other decks, though, unless the 700ZXL's heads matched up perfectly with the other deck's, the Dragon won this one, hands down. The heads were designed to follow the tracks, maximizing performance from all tapes.