Sun 30-Jan-11 09:52 PM | edited Sun 30-Jan-11 10:26 PM by Hotswimmer
If you're determined to upgrade camera bodies then it's a no-brainer - the D7000 is next-generation technology that will serve you for many years to come, and do everything you need and more. It's a better investment than the already obsolete, though still highly capable D90, which would also meet your needs which, quite frankly, don't appear to be that demanding.
Just some thoughts, though this is a shot in the dark since your equipment profile isn't filled out:
1) What about a nice flash and learning how to use it? That can add a whole new element of creativity and beauty to your photography, and does away with at least some of the ISO concerns. There's only so much you can do with available light, and it isn't always flattering to your subject, even when it's sufficiently present. Let me tell you a little something about chasing higher ISO through upgrades, having personally spent over $5000 upgrading from a D40 to a new camera body and buying 2 fast, professional-grade lenses - there's always one more thing you just can't quite do, no matter how much money you spend.
2) What about a copy of Capture NX2, Lightroom, or some other photo editing software, and shooting RAW (or not) and using software to enhance the image, instead of messing around with bracketing?
I upgraded to a D300 from my D40, because I shoot almost exclusively sports under some very demanding circumstances, and sometimes for pay. I needed the additional external controls, ruggedness, faster frame rate, bigger buffer, better metering and autofocus, better ISO performance, and improved color handling of that camera. I would never sell my D40 - it remains my favorite camera when I'm shooting casually, especially when I'm on the move.