Yes. I'll write that.
The CPU is just one small part of the speed puzzle.
Vista is sadly dogging this system and having changed a few too many I can write that easily that gave me back more than a change of a CPU that was 50% faster.
Remember you are still speed limited by video, hard drive and the rest of the system so any CPU speed increase usually results in an 1 to 2 % speed gain given we have to stick with the same board and more.
Why not go for what others have found give you double digit gains?