P5WD2-E Premium vs new Core 2 Duo setups

Guys,

I know that there is a big difference in performance, but I wanted to know if it makes sense to upgrade to a new setup, and will I see a huge improvement where it makes sense to spend the money.

Here is my setup:
Presler 3.0 @ 4.2Ghz
P5WD2-E Prem
2GB PC5300 Geil Gold
2TB RAID 0
X1800XT

What I would get:
Core 2 DUO 6600 2.4 (4MB cache) - $310
P5B Deluxe - $180
2GB PC5300 GEIL??? - I might stay with this
Should I go to X1900 or latest?

Please enlightme...Thanks