New System build, PSU question

So I have a new system almost all picked out. Main reasoning behind the uber mobo and case is longevity and expandability. Anyway, here's what I'm getting:

Antec 900 case (http://www.newegg.com/Product/Product.aspx?Item=N82E168...)
ASRock X58 SuperComputer mobo (http://www.newegg.com/Product/Product.aspx?Item=N82E168...)
Intel Core i7 920 (http://www.newegg.com/Product/Product.aspx?Item=N82E168...)
Kingston HyperX 6GB memory kit (http://www.newegg.com/Product/Product.aspx?Item=N82E168...)
2x WD Black 640GB HDD (http://www.newegg.com/Product/Product.aspx?Item=N82E168...)
LG Super Multi Blu-Ray Disc burner (http://www.newegg.com/Product/Product.aspx?Item=N82E168... ; already purchased)

Right now I'm just going to transfer my existing GeForce 8800 GTS 320MB card for video so I can compare speeds with my existing build (see my profile for system specs) before upgrading to a CrossFire or SLI build. The new GTX 275 catches my fancy but basically my question is:

Assuming I get two top-end video cards in SLI or Crossfire for this new build, what size power supply do I need?

I'm thinking the 850 Watt range using a good quality brand, but I've been out of the "Power Supply" loop for a while and I'm just not sure what the great brands are. I like Antec, but I'd also like to know what other brands are good. Remember I want something that will last me a while, but not something that is overkill for what I'm getting. To clarify, I will likely never have more than five SATA drives (including optical) at a time, and will never use more than two video cards for SLI/Crossfire.