Beginner considering 7D, 6D and 5D Mark II - need advice

I have a 6d and I am really impressed with the low light capability of the camera. I take a lot of indoor pictures (gymnastics and soccer) where flash is not allowed and get pictures that just would not have happened w/o this capabilty (upgraded from a T2i, same sensors as the 7d but not the same quality auto focus). I looked long and hard at the nikon D600 and handled it a lot. The D600 specs are as good or better (and it is cheaper!) then the 6d other then for the high iso capabilty and the gps/cell/tablet capabilty. However, after a lot of reading on the nikon forum the quality control issue was to much for me to ignore. I also think at this level the you are not going to see a difference in picture quality at least 98% of the time unless you are shooting in really challenging  conditions (and this includes the 7d).