Someone Somewhere :
Please post the actual build.
Even with allowance for future upgrades, there are almost no builds that need more than 850W. 1kW is just throwing away money.
This is true. 3- and 4-way SLI and Crossfire is not supported by most games, and can actually give you a worse experience than a single card. In fact, games supporting such builds are decreasing significantly these days.
Even 2-way GPU builds are on the decline.
That said, a 1000+w PSU will run you just north of $200 USD should you want to plan for that type of upgrade. It's up to you, but I really advise against spending that kind of money on something that won't give you a better build.