So, just a quick heads up. I was watching this guy play in a 4k video on youtube.
https://www.youtube.com/watch?v=NAeUvZ5FcKU
He's running a 1080 maxed, and keeping a pretty decent 30 fps. And boy howdy does it look amazing.. but it's running 30fps max. If for instance, Cyberpunk 2077 is more graphically intensive, then say goodbye to playing it on high settings or 4k60 on a 1080.
TW3 looked good enough on 4k to make me think "Titan X Pascal and an UHD screen, or 2x1080 and a UHD screen", though both are really more than I'm comfortable spending.
So many freakin' decisions to be made here! I haven't found anything else on the running-1440p-on-2160p so I dunno where to go with that. I've used UHD with my 780, and it's a dog's breakfast, but it looks amazing standing still. I just don't think a 10xx can do this.. and that's what I've figured was the case for a long while now.