I dont know what you will be using your PC for but its worth noting that you can run celerons with alot less cooling. This means you dont have to have a fan that makes a noise like a leaf blower in your PC
I have two PC's, one is P4 2.5Ghz for gaming and one is a Celeron 2.5 Ghz. I use the P4 for gaming and the Celeron for the internet and work. If you are only using your PC for things like internet, work, music or digital video editing then their really isnt much point going for the P4. You might as well spend the money you save by buying a Celeron on some more memory.