Adding a GTX750Ti to that system will help, but you will still be CPU-limited in some titles. What resolution? I'd expect a mix of medium-high graphical settings up to 1920x1080, except AA and those settings requiring CPU muscle, like greater draw distance (that must track and render more objects).
I was testing GW2 with a GTX750Ti and a 2.3GHz 5350 (that's AM1; much slower than yours), and was getting playable FPS on mostly high settings at 1600x900.