I am in two minds on this one.
I like this guitar, and I really wanted to buy it for quite a while now. But it has some fundamental issues in my opinion. I cannot confirm if those issues are applicable to the particular guitar I received, or the entire GK Studio Negra series. I expect the time will tell if the purchase I made was worth it.
PROS
1) It is a beautiful looking guitar. 2) It is Fishman amplified which is essential for gigs and recordings (but do read on). 3) The finish on the guitar is fine, and 4) the front, neck and the fretboard are well delivered despite this guitar is made in China. 5) The fact it has a truss-rod is a wonderful extra, and one of the reasons I bought it.
It is unfortunate I needed to correct the neck immediately after unpacking, it needed about half a turn, which is a significant correction on a brand new neck (but hey, that's why the truss-rod is there so we're all good).
However, there are other issues I cannot fix.
CONS
This is supposed to be a Flamenco "Negra" model, with warmer and bassier sound comparing to traditional "Blanca". Back and sides being "veneered", or perhaps the way it was put together, is a downside as it practically cancels out the sustain and warmer and deeper sound expected from rosewood. I do not know what is the wood beneath the rosewood veneer, in respect of the sound I doubt it is rosewood (although it should be). The specs just say "Back and sides: Rosewood, veneered".
Ultimately what you get is the Negra looks, with the sound of standard flamenco blanca guitar, loud and snappy, sharp, but no warmth or depth that comes with rosewood body.
I compared it with my inexpensive ¤400+ EUR Spanish flamenco negra guitar which has infinitely more warmth and depth in the tone. So I am pretty disappointed with Cordoba GK Studio Negra in that respect. If you truly need a "Negra" sound qualities this guitar is not for you, despite its name.
Summary
GK Studio Negra is a bit overpriced as well as misleading by name in my opinion. Is it worth ¤649? I would say the build quality is more in the range of ¤450 to ¤500 max, remembering it comes with Fishman and let's not forget the gig bag.
It is ok for practice, perhaps dabbling in Flamenco (if that's what you want to do), and playing around with friends and at parties. Sadly I do not think I can use it for gigging or recordings - which sadly defeats the whole purpose of having Fishman amp onboard.