If you want to stay Nikon for the ease of set up, then the d5300 is probably the best happy spot. Still has 1080/60p, the swivel screen and great performance/colors. You can use all your current lenses and it's cheap! I only have a few Nikon lenses without an aperture ring, but even so, using them for video on my d7100 has never really been an issue. Just pop out of live view, change the aperture based on the exposure meter, then pop back. it takes no time at all really. That said I've also been using Nikon G adapters to use my lenses on other cameras (black magic pocket, and soon the nx1) and everything's been great when using them with the pocket. The aperture control is on the adapter so it's very simple to use/get used to. I think your biggest question is to figure out if you want to stay with nikon and keep everything in one house and simple in post, or do you want to open your options to the wealth of other cameras out there that have excellent features that the nikons don't have, but require a bit of getting used to in post.
