I 5box on a 3440x1440 monitor, only difference is I have a gtx980, so I do have a bit of grunt in my graphics.
However when I first got the monitor and graphics card, I thought I could max out my graphics on all my boxes but too my disappointment I couldn't.
So then then proceeded to lower the settings, but then MiRai released one of his videos: https://youtu.be/J94GQWXTq78 which shows how to auto swap the graphics settings in WoW when you switch toons. This actually helped me out a lot.

So now I get 60fps on my hot toon all the time, but that's because isboxer is limiting them, if I don't limit I can get 150+ fps on my hot toon.

So if you have you troubles with your fps, I highly suggest watching his video. Although you may have to drop some of your settings because your using an older card, you still might be able to keep some of the eye candy.