Which Nakamichi to choose?

It is a good buy if you can still replace all the rubber in the deck; that gets old.

Ok here is my advice on what Nak to get. Get the Dragon or ZX9. another consideration is the 682zx. From what I have read it has a more solid and robust transport than it predecessor the mighty Dragon. You are probably going to have to pay a qualified tech( not just an arrogant overconfident know it all) but one who really  knows the machines. It will cost you. It doesn't make sense to pay $500 to get a lesser Nak up and running to spec when you can find one of the 40,000 Dragon non working been in the closet for 30 years  eBay auctions. But if its just for non critical playback  go for any of the later economy Naks. Maybe all that is needed is a belt.

I heard that Dragon requires more maintenance, and I bet 682ZX records better. ZX-9 is extremely rare and very expensive, great machine, but 682ZX has a classic Nakamichi sound which many prefer. 680ZX is probably the best value overall, though I heard that the bass is not as good as 682ZX's. Can't verify that. ZX-7 is fine too, getting rare as well. I took a look at ebay, prices went up significantly compared even to the last year.

@bstbomber I agree regarding the Nak. ZX-9. Truly a wonderful machine.
I bought a ZX-9 new, back in the 80s and loved everything about it. It made perfect recordings and play back of all of my favorite LPs and gave many years of flawless service.
After a couple of moves, and many years of it in storage (packed safely in it's original box) about a year ago, I dug it out, cleaned it up and serviced the belt and captstins and WOW ! It played and sounded as beautiful as ever.
As I was unable to find my collection of recorded cassettes (nearly all on TDK SAs and SA-Xs) and thinking they must have been in with some other things that had been stolen from my shop - I decided to sell it. A month after selling the Nak, I found (in a box inside of another box of misc. stuff) my collection of cassettes. Now I wish I had it back...Jim

Dragons and 682 can still be had in very good working order, fully serviced for not too stupid money right now.
The 1000zxl and 700zxl not so much! Pretty crazy prices on those pair.
The zx9 is also up there on high prices.

The 682 is probably the best buy out there right now imho.

Plenty of the "lesser" 3 head machines around at very fair money, I acquired my 582 very reasonably for example and for what I want ( to just play back pre recorded tapes) it does its job admirably.