500 or 650W Power supply for new video card?

[BobDaget]

I want to add a new video card to my computer, but the stock one in there is a weak 400W. I am almost sure it will either be a 8800GT or 9800GT depending on what the shop has this afternoon. I can't really afford the top of the line Nvidia card so I have to get something decent, but not the best.
Will I need a 500 or 650W supply? Later on down the road I was going to get another video card as well so I am trying to figure out what the best one is before I spend the money Thanks.

[Bullet Rush]

those graphic cards do require alot of wats , and u already said u got 400 wats ...
if u want my advice , get the 650w and keep it , u never know what u might upgrade later on


good luck !