Best CPU/Video Card combo

[PusherRobot]

I know its all user pref. but is there any truth behind what CPU (AMD 64 or P4) and what video card (ATI or NVIDIA) is a better set, i have all and have moved them all around...but don't have a A64 and was gonna upgrade soon and go PCI-E but i'm not sure if it would be better to go with A64 and Nvidia or P4 and ATI..Just not sure what differences i'll notice.