morgilroka :
It looks like the x4 955 is bottlenecking your GPU. I would recommend you first of all, confirm you're on the newest drivers for your 280x... And if that isn't resolving it, look into upgrading to something like a FX6300(atleast) or an i5
I had 955 BE until a few months ago with a GTX 770 and despite it being an old CPU I never had problems playing most games on highest settings. Borderlands in particular was playing at about 90 FPS.
A new CPU will improve the performance but the reason of his low FPS is most probably badly installed drivers.