Upload & Sell: Off
If you need better AF, and video/audio options/features are going to be important then the 5D3 is your much better option...hands down...as most everything you need to manage the video/audio experience are built in.
If video/audio will be of importance, look at each camera's feature set, determine what you can/can't live without and what possible accessories might cost...built in vs external.
That said, the 5D2 has proven it's professional capabilities/usage for 4 plus years. It's been tested, experimented with, updated, help many build their business and is a top-notch bit of kit.
The 6D uses the latest Canon sensor and does seem to have slightly better IQ and DR, but it's video; at initial release, while very good, does seem to exhibit more morie; much more then the 5D3...there are a few examples on Youtube, I'd research all 3 bodies before buying.
Center point focus is fine on all three cameras, as for outer points, best to kind of usable, it's the 5D3 in 1st place, then 5D2 and 6D following; some report no difference between the 5D2 and 6D.
My best advice, if possible, get to a camera shop and hold/test shoot each body...the 5D2 and 6D use much the same AF system; like your 5Dc does, the 5D3 is a huge, huge improvement.
Here's an interesting Youtube video comparing the 5D3, 5D2 and 6D...it might help.
Canon Full Frame Shootout! Canon EOS 6D vs Canon EOS 5D Mark III vs Canon EOS 5D Mark II