Hello there!
Good news for you: as far as I know, you won't need such an expensive video card for that purpose... but RAM and a powerful processor and massive storage ( infinite layers, instant video encoding and endless movies... ), so an recent midrange videocard seems to be enough ( Mac pro start with GeForce 7300 I reckon...) so, if I were you, 250 euros (nearly the same in dollars) would be enough.
