A r9 270x and a 760 GTX can play BF4 @1080 on a mixture of High/Ultra. For consistent 60FPS on Ultra @1080, a 770 GTX/r9 280x or strong GPU.
That being said, the lowered resolution will benefit your desire to play BF4 on Ultra. I don't think you'll have a problem with that.
I would like to add, buy a new monitor. You are wasting money by playing on a low resolution.