I've got a 2012 with similar specs and it does well for most use, but yeah, video is a beast, especially with the RZX. That said, personally - I'd hold out. There have been rumblings of new models being released this year.
As far as the specs go, 16GB is the max option Apple offers, and that's typically more than enough as memory isn't the bottleneck for video, it's the rapid processing of the video stream. In most of the computers, when running video output like rekordbox, having a secondary graphics driver with dedicated RAM distributes some of the workload. Definitely worth considering, but I haven't done A/B testing of the various options, so I couldn't speak for which one is worth going for.