Honestly what I'd do... Actually it IS what I'm going to do is I'm going to put aside the money to upgrade my video card but I'm going to see what I can push 2k15 to before I upgrade.
My specs are just a bit below yours, as I've posted in this thread. I've been running the FIFA 15 demo in 1080p, high settings, 2x anti aliasing smoothly.
If I do upgrade the video card, I'm probably going with the R9 280. I don't think the 280x is THAT much better but if i find it on sale I may go up to that. That really should be enough to get me through the next few years.