For questions such as this Tom’s Hardware is a web site I have found to be
helpful. A link to a review they did that should answer many of your
questions can be found at this link
http://www.tomshardware.com/2006/09/10/four_cores_on_the_rampage/ .
If you are also upgrading from an AGP to PCI video card and cost is a
determining factor, I would recommend you give a hard look at the cost
comparisons of Direct X10 compatible video cards. The price drop of these
cards in the near future might be more of a consideration when it comes to
what it is you are going to get for and when your dollars are spent
Rich