But... what are your options?
You will certainly need more graphics muscle for triple monitors +, and the 7970 is a very good upgrade from sli GTX460.
Go ahead and buy the graphics card and see how you do. You will get very good graphics performance, higher fps, better minimum fps and the ability to select more eye candy.
Once you are running the 7970, try reducing your cpu OC and see what happens. If the FPS drops considerably, it will suggest that your games are sensitive to cpu capability.
If a cpu upgrade is needed, then a 3570K With a modest OC and a Z77 motherboard will make a big difference.
My only current option is a GPU upgrade, I have $550 to be used for this upgrade and prefer my AMD based system (I just built the damned thing less than a year ago) I'm just sick of having 3 screens, and only using one to game on. I don't even need it to be super pretty pretty in triple screen mode. I can deal with games on a single screen, but would like the ability.
I'm not that keen on replacing my motherboard, and cpu with intel right away. Maybe in another year or so.