Well, thanks so much everyone, for helping me decide what to do. After dithering for almost 2 months, and recounting my money several times, I bought a Nikon D3, gently used for a fair price.
An odd choice you may think, but here are my reasons: I dive the eastern Pacific, in dark waters, I also dive caves in north Florida plus wrecks in south Fla. My favorite shot is close focus wide angle. I certainly enjoy a good macro day, but I always go back to WA. So a camera that excels in low light will give me lots of new ideas for images. And I expect it will perform as well as my D200 in macro, even give me a higher shutter speed.
The D700 is a great camera, but I think I'll get more lo-light coverage with the D3.
Instead of the every-other-year camera upgrade which I've been going through, I think the D3 will last me a long time. I have no interest in shooting video, my husband does that. And I'm not interested in 24 megapixels, I need a more forgiving camera. The "fair price" was the deal-maker.
So I'll be looking for a couple of lenses when the bank account recovers: the 17-35 and the Sigma 150, plus a couple of teleconverters. And then of course, THE HOUSING. Oh God.
Fletcher