Actually it's quite simple, more pixels, more cpu/gpu needed to render the extra pixels, and your system is not "a beast" , i also have a 1920x1080(2073600pixels) native monitor, my system is a dual core amd 2.6GHZ (crap) 4GB ddr3 ram (enough) and a ati radeon HD6550 (more than enough) and i was having a lot of trouble with FPS(15-18FPS) i did all the tweaks in the CFG files, all in-game settings on low, anti aliasing off, postprocessing off, 3d resolution at 88% and even the Ramdisk tip. I knew the problem was my cpu but i have no money to buy a new one right now, i'm saving for a future-proof system. And all of a sudden i remembered that my old monitor was a 1360x720(979200pixels in comparison with the 1920x1080 display it more than half pixels) native and i tought to me: "maybe i can run it with less pixels?" And then after connecting the old monitor i was amazed, literally, now i run the game with everything on normal settings the 3d resolution the same as screen resolution, and no more fps problems, the zombies became easy kills with the hatchet and it runs so smooth and now i have two displays the 1360x720 to play dayz and the 1920x1080 to watch movies and other stuff. So yes u better keep the old monitor to play dayz.