While I did like my 5D2 for files, I couldn't stand the AF on the darn thing. I don't want to do center point, and the outer points would say they locked, and I'd download and find a really soft file.
Is there anything the 7D doesn't do, other than higher ISO is desired? Do you use only centerpoint focus?
Honestly, I'd go with a used 6D if you are a center point AF user- good IQ, good low light focus with that one centerpoint. the 5D2 vs the 6D is sort of a coin flip thing, but as you put down candid's in low light, I'd say the 6D is better suited there, as long as you only use the center point- it is much improved over the 5D2 center point.
Otherwise, if you use the outer AF points on the 7D, then you may want to consider a 70D or 7D2, as there is an improvement over the older sensor. Or hold onto the pennies for a while and buy a used 5D3 if you need good outer point AF - the 5D4 will be out soon, and prices on the other will keep dropping. I haven't found a time where my 7D2 wouldn't lock with the outer points yet, and I even slapped a welding glass I could barely see thru it, and then found a patch of contrast and it could lock. The anti flicker option on the 7D2 and 80D may be of consideration if you have to shoot with available indoor light, and hate each frame being a different color, or half the frame a different color.