As other posters have said - Build!
What I haven't seen noted yet - Skip SLI graphics cards. I went SLI on the gaming machine I built in 2005. What I found was that a top end graphics cards can play games at high settings for a while, and that the extra $450 would've been more effective if spent 50% of the way through the life of the PC (i.e. 2 years later) on another high end card of the next generation.