Dimension 8400 CPU upgrade: Worth it?

So I'm new to the upgrading scene and have decided to see just how much performance I can extract from my Dell 8400 before building my first comp. With the memory slots filled to the brim, new power supply, and a RAID 0 configuration in the works, I want to know if it is worth the time/money/risk to upgrade to the Intel extreme edition (model 670 - 3.8GHz and such). I'm thinking I can nab one for under 130 and it's the best i can get for the intel 925x chipset. Currently I have installed a 530: P4 3.0G

Also, I currently have an 8600GT GPU installed and I've heard that my CPU, given its age, may actually bottleneck my graphics performance. Once I have the memory and Raid controller in place, where I can find more information on testing and alleviating bottlenecks?

You at a spot where new motherboard/processor is needed.. It would be nice to get something a core2duo could fit in.

I personally would sell my gear off, get as much as possible and then purchase the cheapest Nehalem system possible in the next month or two. You are the perfect candidate for a new machine.