Sopolias Falst gave you about the best response possible given the level of information you provided. Computer performance is a mix of hardware (CPU, memory, disk) AND the applications being used.
For example, Av editing (movies, etc) is both a very CPU intensive task and memory intensive. In this case, a CPU upgrade will result in some performance improvement.
How about if you use your computer for writting letters to Granny, surfing the net, and playing MP3s. Will the CPU upgrade have a significant impact on perceived performance? Probably not.
OK, what about doing lots of high-level, compute intensive work on relatively small datasets? Yup, you will see a significant improvement .... your processing time will be shortened a bit. Will it be shortened by a third? Probably not.