Xeon Board I7 950/975 Vs Dual Xeon Quad-core Vs. AMD Phenom II Extreme?

I7 950/975 vs Dual Xeon quad-core vs. AMD Phenom II Extreme? - xeon board

I am a graphic designer / visual that makes a lot of video encoding HD/3D, design and presentation. I use After Effects to Avid, Maya, etc. I want my next computer build, but I'm not sure what processor to go with. I If a i7, use it for 2-3 years and then go to gulftown (allegedly Socket LGA 1366), two Xeon processors, or should I? As far as I know, there is no way i7 or AMD dual-PII based on a single QPI. That's what I say anyway. Ideas?