Nope. performance difference would be barely noticeable.
A while back i've overclocked my P4 cpu from 2.8 to 3.2Ghz (same 0.4 GHz increase you're looking at) and the performance change was not noticeable. Only the increase heat was noticeable.
it would be better to save the money for a new system as even a budget system of a few hundred $ (like an AMD Athlon ii x2 cpu setup) will be many times faster than p4.