Best Nikon camera (Quality)?

I'm not much into photography, I need to buy a new DSLR camera for a friend as a Birthday present. They already have the Nikon D7000.

I have noticed that the Nikon D600 24-85mm is far too expensive than the D7000, I really don't know if these model number express the quality of the camera. (increasingly).

What camera is far best beyond the D7000 in regards to quality, best shoots… Etc.

There's a model D7100 that is 24 megapixles. The D7000 is only 16 megapixles. I think the Nikon D610 is the next model up and it is a full frame camera with 24 megapicles but it cost more than the Nikon D600.