I recently built a system using the Pentium D 830 chip, ASUS P5WD2 Premium board with 1 gig of Corsair DDR2 6400 dual channel ram and SATA raid. I haven’t done any heavy rendering yet, but I have to say I’m not as impressed as I thought I would be. While running Vegas 6 and After Effects simulataneously the perfomance is downright sluggish. Screen redraws are painfully slow. My video card is an Nvidia 6600 PCI-e. I’m still tweaking the system for performance, and may need to add another gig of ram.
If I had it to do over again I might opt for a faster P4, or even an AMD over the dual core. Then again, after I render a long intense project, I may find the dual core the right choice. Don’t know if this helps you. It’s just my initial impressions.