At what lengths are the majority of your shots taken on your current body? As I'm sure you know, 200mm on a Dx body gives the same field of view as a 300mm on Fx, so if you currently shoot mainly at the long end, you might well find that you need a longer lens to catch the action should you make the step up (in size of sensor, if nothing else!) to Fx. Since FPS is a concern, how about the D750? More MP than the D700, higher frame rate than the D8?0s, lighter than either as well. Allows some cropping and still gives decent sized prints (A3+). TBH, almost anything will be an upgrade from a D200 - a decent enough body in its day but rather long in the tooth and showing its age compared to newer bodies!