2GB will be plenty. I would expect you might see only a 10-15% reduction in frame rates AT MOST with the additional 33% more pixels. Your 770 will handle most of the additional work internally with little effort. I run 3 x 1080P monitors with my GTX-780Ti Superclocked/ACX with only 3GB of memory, which is all these awesome cards come with. My 780Ti Superclocked is faster than many of the TITAN cards without overclocking. You will have no trouble. I have everything in FSX set to 100%, EVERYTHING, and I still get great frame rates for the most part. I did go into New York City once with my Ultra-Res Scenery from MegaEarthScenery as well as a bunch of highly detailed airport add-ins for the NYC regional airports, and with the thousands of cars, boats, and planes all around me my frame rate dropped to 7-8FPS. It's usually 17-30FPS (I have target set to 30fps) with the average around 19-20fps. I do most of my flying in very busy areas with ultra-scenery add-ons. When I am out in the normal FSX over most of the world I get 25-30FPS most of the time..