This is what im currently building... taking a while due to the outright costs of the hardware. I only have a couple of the HDDs and most of the RAM so far.
CPU: DUAL Q6600 (Core 2 Quad) (if possible and they come down in price later in the year when im down to the final parts... DUAL 6700s...)
Mobo: Undecided as yet... trying to find one to suit my needs ie. can run dual quad cores as well as have enough PCI slots for HD Tuner and Sound etc
RAM: 16GB A-DATA 800 (will upgrade to more later)
GFX: Dual 768MB 8800Ultra Leadtek cards running SLi
HDD: 2 x 750GB Seagate SATAs running in Raid, 2 x 500 GB Seagate SATA drives
Case: Zalman Fatal1ty FC-ZE1 Case
Cooling: Zalman Reserator 2 Noiseless Water Cooling
And the usual other crap...
Will probably take me about a year to build it cause the case and water cooling alone will be around 1k as will the RAM... the motherboard will probably be the hardest to source as most server motherboards dont have enough of the right type of expansion ports and cost and arm and a leg. But i reckon it will be worth it onces its together and i shouldnt have to upgrade for quite some time...