How much power do these PCI Express cards need?

[blitz16v]

I am setting to build a system with the following specs.

AMD Sempron 64 2800 1.6ghz
1 Stick 1GB RAM PC3200
1 SATA hard drive
Biostar board
X300 ATI, or X550 ATI?

How much power will I need, to safely run this system, after overclocking etc.?

 

[tvdang7]

i would say........... 250w? 300w?

 

[mwmorph]

depends on how far you will overvolt.