I should probably inject some clarity into my comments below about D7000/D7100 choice, and why you might actually need more resolution.
The accepted rule of thumb for printing for display is 300 points-per-inch, so to determine the 'native' print size from your camera, simply divide it's horizontal and vertical resolution by 300 to give your print size in inches.
Thus the D7100 should be easily good enough for 18"x12" prints. But here's the rub: you can get to this size from a D7000 file by only slightly reducing the resolution to around 250ppi.
Such a reduction will be practically unnoticeable at normal viewing distances - chances are a carefully shot and post-processed D7000 RAW file will compare very well to a D7100 jpeg.
So, if you never print beyond A3, and if you're not already routinely shooting RAW, with good shot discipline and are completely competent in your RAW conversion and processing, then the D7100 is probably more camera than you need.