I just tried my new 1070 with the Dell S2716DG and love it - same specs as the ROG and much cheaper (here in US anyway). 1440p, ultra (MSAA only 2x), i'm hitting 144 fps most of the time (in metro, doubt that high outside) and have gsync on. Smooth as glass , no blur even without ULMB. Very quiet card even under load and boosting to 1950Hz without a tweak. Still need to try witcher and see how it does. I'd definitely consider 1440p since getting a 1070 - in a few years when you get a new gpu your monitor will be solid already. Also remember you dont need wuite as much AA at 1440 so not losing much by dialing that back.
Also, agree you can go less on psu but 500gb SSD shoukd be plenty for a long time. That would get you 5 huge games, several smaller games, OS, and programs. I guess if you're a hoarder you might need a HDD.