- Like what you've got: Reconsider. You can get better cameras now (in features and image quality). The one thing still going for the D200 is its small size.
- Dislike what you've got: Upgrade. A used D300 or D300s nets you a modest boost in high ISO work, better autofocus, Live View, and faster card writes. That no longer qualifies as a reasonable upgrade in my book. The D7500 and D500 are the correct DX upgrade choices for you, and which you pick would depend upon what you shoot, I think. A D610, D750, or D850 is a long stretch, and would have you realigning your lens selection from DX to FX.