Yup 850W is plenty. I have dual Tx in my rig (all of the other specs are in my sig) and never go above 620ish Watt during stress tests. Everything is running stock speeds, if I would want to do some heavy OC'ing on all components I'd have to upgrade my psu ofc.
Bit of an off topic question that came to mind while watching the video; I see the 760T running with the top lit on, doesn't that seriously impact the AIO airflow? I would say it would, but it's probably on there for the sake of the video I reckon.