Video card needed for Guild War 2 gaming and future proofing new build

[Soldor]

i5-3570k
z77 extreme4
crucial m4 128gb ssd
corsair hx750 psu
g.skill 8gb ddr3
windows 7

what video card should i be getting to run Guild Wars 2 (mmo game) at max settings with everything on and also be able to future proof my computer for 2-3 years for any other gaming i would want to do. im looking at the radeon 7870 or gtx 660 currently as my budget is in the $300 top area. any help appreciated thank you.

 

[obsama1]

The 7870 will drop to $250 next week.