We do not know enough of what you intend to shoot to give an informed opinion. But you got many nonetheless. Forget all the intenet chatter and complaints, what problems have you seen personally?
If high frame rate is your priority, none of these cameras are what you need. As with any camera class, you can have top image quality or you can have speed but not both at the same time. The D4 or D3s will give you the speed, the D600 and D800 will give image quality. If you can explain your priorities and shooting subjects we can be more accurate in suggestions. I was struck by your comment that you did not want to downsize, are you printing posters or how do you display your photos at close to 8000 pixels across if not downsized and re-sampled? Yes, noise performance improves due to averaging when down-sampled but as is the D800 is not matched at low ISO and at high ISO it will have more color, shadow detail and a finer grained noise than what you are used to. Maybe it would be easier to make suggestions if you describe what is wrong about your D700 that you want to correct with a new camera. Stan St Petersburg Russia