phaisal 0 Light Poster

hi
i am looking for a guide on how to calculate the amount of power needed(the wattage of the power supply) to run a pc smoothly. especially pcs with a vga card. and here is an example of the spec:
cpu:q8400
mobo:ASUS p5g41mlx
ram: 2gb x 1 and 1gb x1 total of 3 gb(as the 32bits os wont see 4gb)
vga:galaxy geforce gts250
hdd:500gb samsung 7200rpm
2 dvd rw
for this spec i am currently using a gigabit power supply full 550 watt and its running smoothly no hick ups or shortage of power and running crysis on gamer level detail smoothly. i jus guess the power from the information on galaxy web tht says this card uses 450 minimum power. but i would want a professional advice on the way to calculate the watt needed