I shoot a 5D Mark II for portraits, landscapes, architecture, etc. I need the 1D Mark IV or 1Dx to shoot sports and dance so my venues can be bright outdoors, poorly lit arenas, dimly lit theaters and stages, etc. I need to capture motion in a variety of lighting.
As for lenses, all Ls: 8-15 f/4, 16-35 II f/2.8, 24-70 I f/2.8 , 50 f/1.2 70-200 IS I f/2.8, and 200 IS f/2 plus 1.4x and 2.0x II TCs
I traded in my 7D for a 70D to limp along with better low light capability. I sold my 7D for $1100 and got the 70D for $949 last Christmas. I just sold my 1D3 to raise more funds.
The 1DX will focus better than the 1DIV in low or poor light.
The X does not have the same focus point illumination in the viewfinder as prior 1D series bodies.
You get full compatibility with the 600RT flash system with the X.
There is little "crop factor" difference between the X and IV.
Based on the quoted post above, I'd suggest the 1DX.
The only ? is compatibility between your 200/2 and the X.