It really depends on what your max budget. A 560 Ti-448 will give you decent performance if you can live with a mix of medium and high settings. I would guess-timate around an average of 35FPS in games like Skyrim which has average GPU demands for a 1st person shooter.
Torchlight 2 will be similar to StarCraft 2 and Diablo 3 so it should not be very demanding at all. Not sure about GuildWars , all I know is that the game is not going to be very demanding on graphics based on preliminary minimum system requirements. However, those requirements can change, and they probably don't take into consideration people playing about 1920x1200 resolution.
Now if you were to play a really GPU demanding game like Metro 2033 or Crysis 2 with the DX11 patch and hi res texture pack then you will probably see average frame rates of between 20 (Metro) to 25 (Crysis) FPS.