The Nikon d7100 has a 1.3x crop mode, which means that it uses a smaller portion of the sensor, but would it have a similar effect as the 1.4 teleconverter?
Did you change to DSLR just to could crop your pictures to get magnification? I doubt it. If you are worried about being too wide, the option I list gives you a choice. A rect. lens requires a MUCH larger dome to get sharp pictures from all I read from others whereas the 10-17 can use the small dome and be sharp.