what is the highest PSU needed for Quad+1VGA?

hi,
i figured because i don't like Nvidia's chipsets heat & Overclockability of Quad Cores i won't go SLI until Intel will bring SLI to their chipsets or Nvidia, maybe in Nehalem.

also, Because of Nehalem i don't want to spend a lot of money on a CPU, coz it's a new Socket of Nehalem.

this is why i thought about Q6600 with is cheaper than e8400 now & a Single Video Card.

but i have a 550W 30A@12v PSU.

what PSU do i need to get for a Good OC of Quad Core & high end Video Card- 9800GTX or the 9900gtx or 4870 1GB (depend on their preformance/price)

is a nice 650W will do the job well? (i think that in the future more cards with 8pins will come out, & i didn't see any 650W psu with 8pin. correct me if i'm wrong)
i don't want to pressure the PSU a lot, to keep it cool & quiet & so it will stay for a longer time.

my main goal is the Corsair 750w as suggested in the forum before. it is the toughest 750W PSU with 60A@12v. but it is pricey.
BUT if this is the best choice for me, i want it for at least 3-4 years, than the price is worth it.

thanks.

Dor.

thanks man. i know about the Extreem PSU Calc.
i will have to wait for it to be updated to 9900/4870 to check + i don't have the pro ver, so i can't see the deviation of the rails- 3-5-12.