I don't understand why people want to use a DSLR as a movie camera. Yes, you can do it and even get a good video. That is not what it was designed for though.
As for dynamic range, I'll assume you are referring to the audio. The T6i has a built in mic and a jack for an external mic; both record in mono. Thus, the DR is going to be crap. It will work for short home movies where quality is secondary and, well, they don't give awards for them.
If you need something with a better DR then I suggest you use a sound board and external mics and then record the sound and video straight to a computer. Or, better still, rent a video camera that has what you need.
Sorry we can't be more specific.