I currently use a 6D as my main video camera. I've used a rented 5DIII and have a little experience with that. I'm not sure how you're covered for audio, but I use a Tascam DR-100 for audio. I keep it separate from the camera and sync in post (FCPX). I'm very happy with the 6D. Every now and then I run into aliasing issues, but usually not. And you can learn how to minimize them with practice. I use the kit lens (24-105 f4) for a surprisingly large percentage of shots. I wasn't planning on using the lens much, but it's extremely useful in documentary and fast-shooting situations. When I have time, I'll use a 70-200 2.8, a Zeiss 50 1.4 and the 17-40 to complement its range (the 50mm 1.4 is magical). I'd get the 6D and put any leftover money into a solid rig, sound system, slider... pieces of kit that otherwise add production value to your video that your camera cannot.