After having heard a few of the Naks, in my opinion, there is very little between them in terms of performance. The 2 headers are equally competent when compared to the 3-headers. A lot of what you would ultimately hear depends greatly on what you play in it.
I greatly respect your view..but i kinda disagree with the general notion that 2 header can match to the performance of three header for the following reasons...
1.)
The head gap profile....The head gap on a two header had to be built for both playback and record...This present a trade off in the head design of record / playback head...This is not the case in a discrete head deck..I do agree the playback on some the the older Naks like 480 , 580 two head dual capstan asymmetrical diffused resonance capstan can come very close to the performance of the three headers...but recording is not nearly as good as a three head deck...
The tape monitoring on a three head deck is a mere feature / convenience.. I think the real reason they were built as three head is to ensure peak performance during both record and playback. This is why some of the earlier 3 head naks were built without the monitor feature..(481,581,660ZX,670ZX)
2.)
Dual capstan / pressure pad lifter... Though this again is not really something that is exclusive to 3 head deck...some of the classic models like (480,480Z,580,580Z) are dual capstan with pressure pad lifter and sound brilliant...The newer generation of generally are single capstan with no pressure pad lifter... As per my understanding the pressure pad lifter server two purpose...
a.) First the scrape flutter that occurs due to the pressure pad rubbing against the moving tape on top of the head is completely eliminated...
b.) Heads longevity.. This ensure that the heads with the pressure pad lifter have superior longevity as the tape is held against the playback head just with intra capstan tension....This the reason why the two head single capstan heads usually wear out prematurely...
3.)
Quality / Material of heads....It is my understanding that the playback heads on all classic transport 2 header / 3 headers came out of the Nakamichi factory line...This is not the case for the newer single capstan two heads on the CR series BX-series DR Series...The general perception is that these were OEM'ed by ALPs...but again there is not proof for this.. more of hearsay...
The playback heads on all classic transport 2 header / 3 headers were made out of sendust...there may be few exceptions...But the two head single capstan nak were mostly crystal Permalloy....
For example, a recording of Pink Floyd's "The Wall" done on a Nak Dragon on ordinary tape, plays very well on my DR3 but sounded horrible when I listened to it on a Nak 1000
This looks to me as if the 1000 was not calibrated to the factory specs...
Also could be partly attributed to a IEC 1981 Prague eq standard change...
To do a fair comparison all units have to be align to factory specs with a information terminals m-300 gauge and a set of reference tapes (speed,track,w&f,azimuth,level,freq response,Dolby, back tension )...
Also most of the classic naks suffer (this is not true for 1000) from orange cap disease (the orange colored polypropylene caps go bad) and these the have to be recapped to get the best performance out of a classic nak...
Again just to re iterate i am no expert in naks...this purely based on my experience on 8 naks that I am proud to own ,had the pleasure of recapping it and re-calibrating it ..and also may be couple dozen more that i have auditioned in various places and also contemplating the views on various forums...