how much power???

I am going by memory for the Athlon @ stock speed:

Athlon X2 4400+...................................72w
1 Typical 7200RPM HDD..........................15w
1 DVD Burner........................................15w
8800GT (stock speed)............................85w
2 Typical 120mm Fans............................12w

Total Power Consumption on 12v rails.......199w
Total Amp Consumption on 12v rails..........16.5a

All other components draws power from the 3v & 5v rails and is not as important as the 12v rail since power draw is relatively low.

Any decent 450w PSU will provide at least 26 amps on the 12v rail. My brand recommendations are as follows:

Seasonic
Corsair
Enermax
Antec
Fortron (FSP)