Don't get me wrong, I agree that Quad Core is on the higher end (obviously).
My only concern is cost difference (not sure off top of my head) versus performance gain. I don't do a whole lot of encoding, hardly any at all, but I would think the difference in cost versus what is gained just isn't worth it until the actual software can take full advantage of the quad cores.
I'd like to see some real world benchmarks though comparing the two. Seem to remember reading an article saying that the C2D EE QX6800 is better than some of the Quad Cores, will try to find that article if I remember where I saw it...