I don't understand this whole 4gb issue? No problem with my Gigabyte Xtreme 970.
Play a game using DSR at 1440p and look at your VRAM usage. It will never go above 3.5gb as the developers have coded games that way for the 970.
I get decent FPS at 1440p with my 970 bit sometimes it goes below 60 hence thinking of getting this Dell monitor