[prodigalsquire]

In my opinion, lenses matter more than bodies, the better the lens the better the images. All that out of the way, the question I would ask is:

What else besides your tank(s) are you looking to shoot?

Personally I shoot a lot of wildlife and nature, so my two big concerns were shutter speed, and pixel count. I ended up with a camera that can hit up to 22FPS and has a robust Auto-focusing system, I can shoot everything else with it, but it excels at capturing the unpredictable action of wildlife. However I can turn around and shoot a model in my studio with the same camera, and the images are great.

Most pro-sumer DSLRs are pretty similar, and for "general purpose" shooting you wont see much of a difference, but each one does one or two things better than the others, and that is where you can make a huge difference.

Beyond that I shoot Canon, so I cannot give you model advice for Nikon.

Good luck and happy shooting!