The only difference is that one has VT and the other doesn't.
VT is useless IMO.
VT, A.K.A. ViiV
And I do have a Pentium D 945 OC'd to 4.51ghz as my 2nd rig, http://valid.x86-secret.com/show_oc.php?id=110762
That version of CPU-Z red the CPU as 950 but it's a 945.
Save the money and go for the 945.
JP, Core 2 Duos are not compatible with P5WD2-Premium unfortunately.
What sort of cooling setup do you have to reach 4.5 ghz? I have pretty damn good aircooling with a Tower 112 heat sink and big fan for this cpu. Think it will be safe @ 4.0ghz? I'm willing to go a bit farther if thats a safe range