it depends on wat all hardware u have. . pc's without OCing and g-cards can often run on local 450W smps costing around 500 bucks or those that come with cabby's
those having low end orlow power consuming mid end cards with no OC and low power consuming proccy's will also be satisfied with the above smps
but they run better on 500W smps costing around 2k
(zebby , powersafe , colorsit etc..)
pc's with higher end gfx cards will need 450-600W smps costing around 4k
(cooler master or corsair )
will u want to OC like hell , have SLI setup of 2 high end cards , then
u'll have to go 4 >4k models from antec , corsair , cooler master etc..
also , remember that wattage is not all . efficiancy is quite important .
and most of all , the amps on the 12 volt rails is very very important.
pc's without g-cards generally need around 20A . mid end g-cards - 22A (and better efficiancy )
high end - >26 or 29A . . . sli setups will need a lot.
furthermore , guys with 4-5 hdd's , 2 dvd drives , a lot of USB devices may need a bit more power.
