Betwenn the X23800+ and the X25000? Yeah... there is quite a performance increase. What are you going to be using it for though? Chances are a 4200+ or 3800+ is good enough for your needs.
An X2 3800+ is good for the price. If you got the cash, just save up for the Conroe. In your sig it says you already have a X2 5000+, so is this for another computer or something?