the p4b has a front side bus of 533 and the p4c and p4e(prescott-curse the name) have a fsb of 800,the fsb is the general performance of your cpu,so the p4 c's are better and have better(faster and more advanced mobos);but the p4c's and e's have hyperthreading(which some people hate and offers no gaming advantage),the p4 c's are better than the prescotts and overclock well.
If you've already got a p4b,with a fsb of 533,it's not worth upgrading(unless you're rich).You might not be able to tell the difference in actual gaming as opposed to benchmarking,just as some see little difference between their amd xp systems and amd 64 systems;but then again maybe you can...
