Just so you know, you can only change the FSB on the ASUS. That may limit how much you OC, depending on the rest of your rig.
Edit\\\\ I was looking at the ASUS P4S800-MX. It may be wrong, but the link I gave you before says that there NO OCing options in the P4P800-VM.
Edit2\\\\ It's confimed, there is no OCing options in the P4P800-VM