Hi newcomer and welcome to the Tom's hardware forum.
You can get a better performance with upgrade the CPU, but bear in mind this points:
1- You need be sure that the processor is supported by your mobo.
2- Currently I have a X4 955 in a mobo socket AM2+ and my HT is 2000, but the HT isn't very important as the CPU FSB
3- You new AM3 processor support DDR3, but if you install it in a mobo AM2+ only can use DDR2, that can reduce the performance.
4- Not all the performance on games depends of the processor, you also bear in mind the GPU and RAM.