System specs:
AMD FX 8350 8core 4ghz
12gb ram
Windows 8.1 Pro 64bit
NVidia GeForce GTX 550 TI
256GB SSD hard drive
50gb up / 7gb down Cable Internet

Currently I have to run on custom settings lower than even low settings to run optimal in dungeons. Outside dungeons I run 60-90 fps. In dungeons I run 30-60 fps. And in Titan hard I run 20-30 fps.

I'm looking to upgrade my video card to raise the fps as well as my goal is to run max settings with steady fps. Suggestions?

Currently I have been looking at Radeon 7970 , Radeon R9 270x, and GeForce GTX 670. but not sure which of those if any would be a good choice.