you're not gonna get the exact wattage... it's always a bit less. regardless the unit dustin posted the link to would probably be fine, Corsair makes solid power supplies... plus it has a $10 rebate from newegg.
Yeah, it's the manufactures rebates not Newegg. You fill out the form and supply the other info required, and no check ever comes. After some 200 Newegg orders, I have only returned one bare-bones computer and one motherboard for a refund. I just don't go for rebates any longer. Free shipping is another story though