I would go with the premium BenQ. You can use your old monitor in double for productivity, and you can just gave on the 144Hz one. 144Hz gaming is like a 4K TV, sure it sounds good, but once you see it in real life you realize it is pretty badass. (That being said, 144Hz is only noticeable in games with quick action and fast movements, so we're not talking about Civ 5 here :P )
Update: Another option, a 2560x1440 monitor is good for gaming and is a productivity beast.