IllegalPaladin on 07 February 2010
You're other option for the OS would to get the OEM version which are cheaper than the full versions, but it'd be like what you get from hardware vendors as in the OS is tied to the motherboard and if your motherboard fails and/or you replace it, that product key will be worthless.
The $1500 one you linked in your post also used 2 GTX 260's in SLI. Like I said, I just pulled together some things really quick.
It's a little better for somebody who already has certain things like an OS, keyboard, mouse, speakers, hard drives and DVD burner/rom than somebody who's starting from scratch.
@Killergran - Go for the fan overkill with Antec! :P
Essay Pro