Top of the line components abound, but, I'd prob trim the cpu back to a "mere" Opteron 180 (dual 2.4 vice the FX60's 2.6), saving you aboout $300....
(In gaming at relatively high resolution, even with a top of the line card like the 1900XT, the video card will be the most important and will still be a bottleneck; in fact a 4200+ will likely score nearly identical framerates as an FX60 in most gaming titles)
You could probably even save another $80 by opting for a Crossfire board over an SLI board, or even a single slot NF4 variant, although the Asus SLI you've chosen is indeed one of the top Two mb; it just seems a shame to pay nearly $100 extra for an SLI variant incapable of running SLI...
You could also trim the mem back to two each 1 gb modules, saving another $200, as most games are happy with 2 gb...
(Now you have saved $600, allowing a free purchase of yet another killer video card in 1 year..)
All of the components are awesome; I am merely trying to trim $400 of of it for you, and still have your new rig deliver 99% of the framerates possible in 99% of todays games for $400 less...; but, if money is no object, you should be pleased for two years, easily, with the parts you have chosen!