I would second the GH2. With the Driftwood hack they can shoot very high bitrate. Even standard you get amazing looking video out of them.
The BBC in the UK use them for certain shows and they're notoriously strict on what cameras they allow to be used.
I second the GH4. I have mine a year at this point. It's a very versatile camera that has never let me down. I've shot films, docs, events & news pieces.
Great video, robust build; mine still looks new with plenty of hours racked up on it, almost every lens ever made fits with cheap adapters.
My personal opinion would be the GH4. I've been using it a year now and I haven't run into any problems with it. I've shot short films, feature films. events, documentaries and used it for video journalism so it's quite versatile.
The GH4 only shoots 96fps compared to the 120fps of the NX1. If you need the 120fps I would go with the NX1. I personally wasn't a huge fan of the colours the Samsung produced but everyone has a different taste of what they like to see.
The main factor for me would be lens selection. I believe the NX1 doesn't really have a huge variety while the GH4 has a ridiculous amount of choice and adapters and most are quite cheap.
I think what the decision really comes down to is you. You know what suits you best. I think go with what you feel is better for you and your projects. I got the GH4 over a7s simply because it suits my style and what I use it for. A colleague of mine got the a7s as it suited his needs more. It sounds like you really like the Samsung and if it fulfilled your needs, go for it.
I would recommend the Panasonic GH4. I run a film, TV and video production company here in Ireland and I use it for the majority of my shoots.
It's small, versatile and very easy to use. It has a small but high resolution sensor which I've never used on green screen but I have seen videos with quite good results.
With the money you have you could get a GH4, lenses and a lighting kit. Also some high speed SD cards.
@Ben James, Invalid point. You don't take a copy of the Ferrari that was given to you.
@Guy, I hope it's as low priced over here. Unfortunately Ireland seems to have a magical way of getting higher than average prices. The cheapest I got quoted here was €108 which is around $120 or thereabout.
I'd pay for 10bit 422 straight away. If V-Log is reasonably priced I'll definitely pay for that too.
Take a photograph with a flash from outside the window