Yes, having two more cores (12 threads instead of only 8) makes a nice difference with my editing. I set After Effects to run only 8 threads at a time, saving the last 4 for other tasks, and now I never crash during intense renders. Premiere briefly showed it was using 1205% of the CPU today, which surprised me, since it only has 12 threads, of course. Perhaps they were in turbo boost or something. The biggest improvement I made was installing 4x8GB RAM and the external 8-bay RAID, but I believe the 6-core has been the final piece of that made the system more stable overall. My original CPU was the quad 3.33GHz W3580, so bumping up to the W3680 didn't make single-threaded jobs any faster.
Standard Definition footage is super easy to work with, so you shouldn't have any problems with a quad core.
RAM is cheap, so get 32GB or more and you should have no problems with Photoshop or Lightroom. I try to avoid Bridge. When I use it, I only have it open for a few seconds tops, and quit it the moment I'm done with it.