Get the x1950Pro, much better card.
Your CPU will not bottleneck the card, especially if you're playing at 1280x1024 or greater resolution. Or if you tend to play with many of the goodies such as AA and AF turned on and high or max details.
Now if you were planning on playing everything at 800x600 with lowest possible setting there is a small chance the cpu could start to come into play but I doubt you're doing that so no worries, get the card and enjoy the improved performance!