I bought Voices of the Aztecs and Voices of Istanbul, and after annotating their contents in my humongous sound sources document (now several hundred pages long), I found that almost everything in these two libraries required new entries!
A month ago, there was a new Turkish library released by a new vendor, but it is super-expensive (I can't remember if it's $300 or $600). I will eventually buy it, but even once I do, there will be a lot of instruments in Voices of Istanbul that are unique to that library.
The only other library that has even a tiny amount of overlap with Voices of the Aztecs is Eduardo Tarilonte's Forest Kingdom for Best Service/Yellow Tools ENGINE sample player.
Granted, as these are old libraries they faced the sample size and library size restrictions of the mid to late 90's, but they are very well played and good miking and recording techniques were used, so I would say they are better resolution and more detail than mega-libraries like MOTU Ethno or Ethno World. The prices are low enough that they're worth it even if just for a couple of specialties.
Audio Deluxe is selling most, but not all, of the Q Up Arts libraries, so loyal customers will get somewhat of a discount there, but the vendor's site has discounts at the moment as well as a bundle for the Native American libraries, and the Aztec library is only available there.
I owned the Turkish library in Akai format many years ago, before I had a computer, and almost had a nervous breakdown trying to manually convert it to Yamaha MOTIF format. I almost bought a used Yamaha A-series (3000, 4000, or 5000) sampler to help automate the conversions, but ended up deciding that might time could be spent on more important things, so in many ways this library is what finally pushed me to buy a computer instead of doing everything off-line.
