I was originally leaning towards the monitors with higher refresh rates, but my friends reeled my into IPS technologies so I got interested in that too. Now I am in a though decision on what kind of monitor to get. My current monitor is a basic 24" 60 hertz Asus LED monitor.
Price is not too much of an issue (although I would still like to know which is best bang for your buck) and I play many games from FPS to RPGs but most of my FPS games are older/non graphic intense such as CSS and Crysis 2 (and things between that level of graphics). Recently though I find myself playing more non FPS games.
My specs are as followed:
I'm sure you can get a 1440p panel for that price. As a user of a 120Hz panel, it doesn't really make much difference if you are playing single player games, the extra FPS and responsiveness are perceivable but you only notice them once they are taken away. If you are into online FPS's and stuff it will make all the difference in the world.
Another possibility is 3D if you care for it, you have an Nvidia card and any of those 120/144Hz displays support it.
If you want my opinion, depends on how much FPS your 570 can generate at your preferred settings. the higher it is, the 120hz is more attractive. IPS is always a solid choice regardless due to color. neither is necessarily always better than the other, its all about preference, fluidity vs vibrance
I vote IPS or PLS. I'd notice the lack of quality far more than the lack of response. And if you get an ASUS model (like the MX279H you're looking at) with the Trace Free feature, you get best of both worlds - exceptional quality and fast response. Be aware though that's a 1080p 27"er so pixels will be a little larger. I'd recommend these:
I personally prefer 120hz. Not just for the added smoothness, 3D and responsiveness, but I actually get sick using 60hz lcd monitors if I play more than 30-60 mins. If you have motion sickness/simulator sickness issues as I do, the benefits of 120hz are hard to ignore.
I went with the Asus 23" MX239 IPS and honestly I tried some of my games out on it and it has very vibrant colours but it's very dark which I can adjust in the game, but then when I got into something like a web browser its too bright and I have to readjust. Not exactly blown away, may return it and try a high refresh rate monitor, or even stick with my basic monitor to avoid more hassle.
I wouldn't stick with something you're not happy with, but just make sure it's not simply wrong settings. Gamma can be controlled in the game settings and in nVIDIA control. Colours can be adjusted on the monitor itself and in nVIDIA control panel. Obviously brightness and contrast are on the monitor itself and you may have software controls also. Best thing is to get your Windows how you like it and then adjust the gamma settings in games.