I've been toying with the idea of keeping my dual quad core rig until the next generation of processors and RAM come out. I currently have a 1200w PS, GTX480, and two new 1TB HDs to add to my 2 x 2Tb RAID O(not in the same RAID 0 setup, of course!) . I know the big advantage to a 980x setup is the DDR3. Of course with dual quadcores, I have DDR2. Anyway, my concern with keeping my current rig is that the PCI-e slots I have on my Tyan server board are two (2) PCI Express x16 slots (X16 Gen2 signal from MCH). I take it this is slower than the current PCIe 2.0 x16 standard. I would appreciate feedback as to whether this might significantly hamper the MPE performance of my GTX480 if I stay with my current setup. By the way, I haven't installed CS5 or the GTX480 yet or the 1Tb HDs yet, for I'm not totally convinced the extra almost 3K to build the 980 rig is a bad idea... My main editing workflow right now is :30 commercials, HDV footage with 1-12 layers of video tracks, mostly text layers or 1 AE comp. Hoping to upgrade to AVCHD-intra some day...
The Ram is really where the performance hit will be with your setup when compared to the I7 configuration. It really comes down to your editing and deadlines as to whether it's something you need to upgrade now. What you are adding will help some but not nearly as much as it would with the I7 setup. Your ram is like a central communication hub where everything goes through. The performance increase alone with the ram bandwidth on the I7 will be several times faster than the DDR2 system.