I would say the E4300 or E4400.
They are cheaper and will result nearly identical performance when OC'd.
In fact, either CPU will likely give you more power than you need.
My E4300 is running at 3.0Ghz.
I was able to run 3.2Ghz, but under load I could hear my CPU Fan.
At 3.0 Ghz, its almost completely silent all of the time.
Even though I do many CPU intensive tasks, I cant feel the difference.
Take the money savd and upgrade another component such as the GPU which will yield a more noticable difference.
Or take the money saved and hit the town one night.
I seriously doubt you will see a difference.
Where you will see a difference is in the new 1333 FSB chips that are shipping. They will be able to hit new OC levels thanks to the new stepping.
You will however, need very fast RAM (1066+) and likely a P35 mobo to reach the FSB to really push these chips to the limit.