Its not always a 'cut and dried' A is better than B situation. What programs/games do you run?
If you like gaming - what video card are you using?
And mention what motherboard you have that E6700 on.
Im guessing a quad core upgrade would be a marginal upgrade unless you're heavy into audio and video work.
Good points. My vid is 8800 GTS 640 MB. Some gaming (Far Cry, etc), but vast majority of work is Powerpoint, iTunes, standard Microsoft Office worker bee stuff. I just really love having a quick response out of my computer. So, upgrade or stay put (or overclock)?