Not in guild wars :P Not many games use PhysX so its not really benificial. What i would suggest is look for reviews of the card you want to get and get the one which performs best out of your price range, some games prefer AMD to Nvidia and visa versa, so do some research before your purchase
NVIDIA vs AMD
These are the games that currently use PhysX:
http://physxinfo.com/
(you can click the blue i icon next to each one to see more info and a youtube video of the corresponding PhysX effects)