Hello shaithes
Going from 1920 x 1080 to 2560 x 1440 you'd see double the picture quality. Being that both monitors you're looking at have IPS panels they will have better color accuracy over your current monitor which has a TN panel, so that will also improve picture quality.
Going from 2560 x1440 to 3840 x 2160 will double the picture quality once more so going from 1920 x 1080 to 3840 x 2160 will be four times the picture quality.
A GTX 980 will suffice with pg279q but you probably won't hit 144 frames per second in most games but as long as you're hitting 60FPS or above you will have smooth game play.
One GTX 980 isn't enough horsepower for the pg27aq, you'd need at least two or even three gtx 980's to hit 60FPS in most games and with the GTX 980's 4GB of Vram it's really not enough, so while the GTX 980 is still a good performer it isn't up to standards for 4k gaming.
My recommendation would be to add another gtx 980 for the pg279q to get you up around 144FPS.
If you go with the pg27aq, then you will need a gpu upgrade of at least two 980ti's or two titan x's, if you can afford three then all the better.
🙂The main difference between a 60Hz monitor and a 144Hz monitor is with a 144Hz monitor you will get no motion blur with higher frames per second.
A 4k monitor and the hardware to run all games at 60FPS is a dream machine. As of right now all 4k monitors are 60Hz and is due to the limitation of displayport 1.2
