Focus more on technique, lighting and a good macro setup, be it styrofoam plate diffuser or ring flash, reverse macro ring or Voigtlander 125mm macro.
Depending on what you have already, a D7k will only likely bring 2-3 advantages to macros:
1. Better dynamic range to recover highlights and shadows.
2. More megapixels so that you can crop more from the existing magnification
3. Lower noise at higher ISO so its less stressful on the flash power/aperture/ISO trade offs when shooting small aperture for macros
Most of the three can already be off set to a degree by better technique/setup.