I don't understand, jim. What is there to be gained from running at 4k resolutions but having poor details? It will look awful and will be made worse by having exaggerated jaggies because I'm assuming AA will be one of the sacrifices along the way. As Repressor points out, going with a lower res and scaling is a better option (and sometimes it negates the need for AA sometimes, the pixels get massaged

)
I would have a look at the following article;
http://www.guru3d.com/articles_pages...review,23.html
It seems possible that anything around a 680/770 or a 7950/70 will be able to push past the 'playable' 30FPS, since they already sit around 20FPS with settings maxed out. But what a 'playable' frame rate for you might more than 30, it is for me.

However, at normal resolutions, a greater than doubling of frame rate is not uncommon with shifting settings so... ¯\_(ツ)_/¯