I currently have a 60D. My primary usage right now is kids sports, mostly lacrosse with some basketball mixed in. My oldest plays most of her lacrosse games at night. I have been using a 70-200 f/2.8 IS MKii. I'm using shutter priority with ISO set to auto and find that most of the night pictures are taken at ISO 6,400, which seems to push the boundaries of the 60D's capabilities.
As a novice who never expects to make a living at this, I can't justify the 1DX or 5D3. From what I have read here and other places, it seems as though the 70D is the logical choice. With that in mind, two questions for the experts:
1) Would the 70D provide meaningful improvement over the 60D in low-light sports environments?
2) If my budget is $1,000 - $2,000 is the 70D the best option for my needs vs. a 7D, or used 1Dxx or 5Dxx?