The Core 2 Quad is dead technology. It's still a capable processor now, but the socket 775 motherboard it sits on is now obsolete and being phased out.
Get the i7 920 as that tech has a long life ahead of it.
I'm more than happy to suggest a spec for your video editing needs.
A note on your graphics setup: I don't know if the driver "issue" has been resolved, but you can't use a NVIDIA card for dedicated PhysX if you're using an AMD card for graphics - the NVIDIA driver blocks it.