graphics card
It won’t have amazing FPS but it can hold it’s own if your expectations are not super high.
I’m not sure if you’re getting some special deal on it, but I would suggest to invest a bit more if you’re not. GW2 doesn’t need too great of a GPU, but you might want to play another game too that could be more GPU-bound, and it’s never a bad idea to leave some headroom so your card doesn’t run at full speed constantly. I’m seeing it going for about $75 at lowest, whereas for $100 you could get something like this: http://pcpartpicker.com/part/asus-video-card-hd7770dc1gd5v2 which gives you over 2x the performance on paper with only $25 added to the price.
i5-4670K @ 4.6 GHz | GTX 660 | 8GB @ 1600MHz | Samsung 840 EVO 120GB | Win 8.1