If you're only going to play those two games, I suggest you get a 8800GT/9800GT instead. You will get bottlenecked by your Pentium D until you overclock that processor, or raise the resolution, which I don't think you'd do. Or, as lava said, you can always get the 8800GTX/9800GTX+ and put the settings to the highest.
Pentium D 805 processors should easily hit 3.2Ghz. Try it and see what happens.