best amd processor

Solution
Thats an Intel socket 775 board. There are no AMD cpus that will work with it. Here's a list of cpus that board supports.
http://www.gigabyte.us/products/product-page.aspx?pid=3743#


Sorry, but you are very very wrong here.
That's a socket 775 Intel board, Always go back to the website of the manufacturer.

http://www.gigabyte.com/products/product-page.aspx?pid=3743#
http://www.gigabyte.com/support-downloads/cpu-support-popup.aspx?pid=3743
 


if you read the message I said " if you meant your board is Gigabyte GA-G41MT-S2 (rev 1.3) "
I never said -S2P. I agree my suggestion was the wrong one, but I did put it in proper context.
you in fact found the right one...
 


The one you suggested is also 775, the site you refer to calls it an Intel chipset.