Which Nakamichi to choose?

Thanks, @terry9 . I still have my notes on the various Nak models when I was looking to buy.
I worked in studios and am very familiar with how quiet R-R and cassette can be. I'd like to try transferring CD's to a high-end cassette deck; I know analogue tape bestows a nice sonic quality to the recording.

While they certainly SOUNDED wonderful when compared to vinyl back in the day--a "hollow" sound was the most notable difference when compared A-B to vinyl--my personal experience when selling Nakamichi was that 100% of them came back broken within a few weeks.  They were sent off to be fixed and typically were OK after that--the 700 was particularly quirky--but the others were OK.  Dragon (II?), I think, was considered the best one at 3 heads, but the various versions of the 700 and 1000 had 3 heads as well as I remember. (Getting old!)

If you get one, be sure it has been serviced and listen to it A-B with another source--vinyl suggested--and you might be surprised how good it sounds when it works.  Regarding good tapes, I have lost track of that medium, but it is not an inherently bad one. I would guess people here know which ones are considered "best" today. Now DIGITAL...don't get me started on compression algorithms.  UGH!!

I researched cassette decks from ebay 3 years ago and found "best value" deals on Nak CR3, one of which I bought and tested for a friend. It beat out the SQ compared to my refurb Teac V770 (which I also recommend) and to a JVC 3-head deck TD-V621 (which I bought for myself as a backup; not bad but not as good as Teac or Nak). I thought that most of the Nak 3-head decks circa late 80s-early 90s all looked good, but some were going for a premium price. The decks I considered were CR3,CR4,CR5,DR1,DR2,DR10, and Nak "Cassette Deck 1". A full refurb on any of them would be good to consider IMO. PS the CR3 finally broke down after 3 years according to my friend. No repair shop nearby where we live...

lowrider57

Proper bias is of course very important, but would you archive vinyl using Dolby?

I wouldn't choose to archive anything on cassette. It's just not an archival medium.

Had a Naki 600 back in the day. Only 2 heads but was impressive none the less. Got stupid and sold it. Had a 680 ZX for a short while which was also a quality device. Sold that as well. Regret that simmered over the years resulted in my finding another one - a 600 - and buying it from a fellow in Canada. 
Still sounds remarkably good with a quality tape such as TDK SA, Nakamichi,  Maxell EXII, or Fuji. Of course it couldn't tranform a sonically-poor LP into something good, and care had to be taken to not 'over saturate' the tape when dubbing.
Still sounds great in my 1988 BMW's stock cassette deck based audio system.