"Future graphics cards" or "what if SLI" is a poor excuse for a ludicrously overkill PSU. Power requirements for upper-middle class GFX cards have not increased several hunders of watts during the last few years, usually the next GPU generation gives more power for roughly the same wattage.
Sure, if you are going to run the ridiculously power-hungry, not to mention overpriced "best card ever - for the next two months", or two, then you will need that miniature nuclear plant. However, if one needs to ask for a recommendation, one is hardly going to go for those alternatives. SLI/Crossfire is just double the waste of money. Hello, it won't keep your system fastest on the block long enough to be a sensible investment. By buying the "next best thing" that's almost as fast, at a fraction of the price, means that the mighty 1 kW PSU will be idling even under full load.