So I'm looking to upgrade my Mac Pro to a better processor. Either of these processors would make a word of difference to my Mac Pro. Question is, do I go for the higher clock speed, or the hex-core processor? Here are the options: Nehalem, 4-core, 3.33GHz, 8MB of L3 Cache (W3580) OR Westmere, 6-core, 2.66GHz, 12MB of L3 Cache (X5650) Currently, I have: Nehalem, 4-core, 2.66GHz 8MB of L3 Cache (W3520) Basically, it comes down to the clock speed and cache. Right now, I this is my main machine and I hope to use it for video editing and rendering in the future with Final Cut X. Right now all I use is iMovie, and a few other apps such as Safari, iTunes, etc. Basic Mac stuff. I'm still transitioning from iMovie '09 to X, but I mainly use iMovie X now. Now, I know iMovie is multi-core aware, but will it use all 6 cores? And at that point, would the clock speed mean more then the amount of cores?