Mugz :
Minimum 750W, depending on graphics card(s), hard drive(s), and other equipment/accessories/etc.
And yes, I am a firm believer in overkill.
OK here are the components that i might buy
MB - ASUS Crosshair IV
CPU - Phenom II X6 1055T
RAM1 - x2Kingston 2GB 1333 MHz
RAM2 - x2 Kingston 4GB 1333 MHz
SSD - OCZ Vertex 2 60GB
HDD - Seagate Momentus XT 250GB
HDD2 - WD Caviar Black 500GB
GPU - MSI Cyclone 4890 1GB
CASE - Gigabyte Aurora
ODD - DVD RW
COOLER - CoolerMaster V10