onboard video with GA-8I945GMF

How much of a difference will their be with the onboard video with a the

Gigabyte GA-8I945GMF Socket T (LGA 775) Intel 945G Micro ATX Intel Motherboard

and the

Leadtek WinFast PX6800 TDH Geforce 6800 256MB 256-bit DDR PCI Express x16 Video Card

I am planning on making a computer for gaming, Counter-Strike:Source to be more exact.