for the money, and since you can potentially use your current Canon lenses, I don't think you can beat the quality that can be had from the BMD CC. For $2000, it really seems like the best video camera you can buy (for the non 4k version). The only drawback really, is you will also need to spend another $400-500 on a good camera rig, since out of the box, the BMDCC has absolutely no ergonomics. But even then, you are still under the MSRP of a Canon 5D MK3. The MK3 is certainly a fantastic camera with great low light performance and an incredible amount of third party support and user base, but I agree that the video is a bit soft and the H264 camera encoding is not exactly ideal. I believe the BMDCC can record straight to Apple ProRes which I would absolutely love.
Another option, if you were alright with losing your lens carryover, would be the Nikon D600, which is one of the highest rated cameras of the last 5 years. It will likely be my next camera purchase since I've already got a few lenses for my D5100 and the price has come down quite nicely, resting at around $1500-1600 brand new. They've got a D610 out now, but I don't believe it adds enough over the D600 to make the much higher price worthwhile.