I use an additional screen to display the GPS and some extra displays (outside look of plane). I am running it at 1920 x .... - I would like to build to Eyefinity soon but quite confused about it. I don't know what kind of additional device i'll need.
You just need more monitors, preferably one that supports Displayport. Just plug them in and tell CCC that you want to create a display group.
I wouldn't think that an additional screen with that stuff on it would be all the more stressful, but you should disable it and see if your performance changes. If it does, then you need more GPU, if it doesn't, then it may still be CPU bound (I know, hard to believe).