What do you plan to do with your computer? If your not running programs that will benefit from the extra cores, you probably have no need for the 6 core and can save money by getting an X4 instead. Or if you gaming, I would recommend getting an X4 and using the money saved on a better video card.
And windows 7 does a good job scheduleling tasks to the cores, if anything it's Xp that does it poorly. lol