Heya Tommunist;
Well my friend the best advice i can give you about upgrading your computer is, your computer is only as strong as its weakest link which is usually the motherboard, in my oppinion you should always upgrade the three major components at the same time.
These are Motherboard, CPU and Ram, if you do that and buy good quality hardware from companies with a good reputation for excellence you will always come out of it with a smile on your face.
I would suggest buying a dual channel memory motherboard they are monsters in performance and its there that you will see your largest performance increase, much much more then just buying a slightly faster CPU, even if the FSB happens to be a bit faster, however increasing the speed of your Front Side Bus will also yield nice performance increases. In most systems the largest botle neck of performance is the memory bus, and if you upgrade to a dual channel DDR board you will see marked improvement worth spending the money on.
If you are gonna upgrade then do it right just build a new core, you wont regret it.
I know you want it and you want it now but when building a computer it is always better to do some research, find the latest and greatest, save up some cash for awhile and do it right.
I hope i have helped.
XeeN