I would recommend that you tackle your pleasant dilemma in one of two ways:
Jot down, in order of importance, the features that you require from a camera, firstly have-to-haves and secondly, nice-to-haves. Having completed that list, compare your list to the features of each camera, using that to select the MOST APPROPRIATE for your needs and desires.
Alternatively, list, from the most to the least important, the TYPES of photographs and environments you find yourself, which will give the rest of the forum the background needed to help you make a better informed decision.
Each of the D600 / D7000 / D7100 has its wow factors and its downsides, relative to the others. For example, if speed and buffer size is top of your list, the D7000 is best; If low-light is your thing, the D600 cannot be beaten. The D7100 is great for sharpness as it does not have certain filters, BUT it may CAUSE moire when photographing certain repetitive patterns.......
Each to their own, but they are all very good cameras.