What are you asking?
1) do you need a bigger power supply, for what....
2) if you know the answers why are you asking hte questions?
If you are playing with DDR2 than I doubt you need more than a 850W. If it was new in your life time. If you bought it used, than I hope you have a good means of testing it
Anything you buy used you should have a good means of testing. Otherwise do not save the money (it will be heart ache)