Ehem... people who aren't sure of what they're talking about--you can go now. Anyways--here's the absolute best that you can get with money (and power draw) being no object. You'll have to do a little bit of hunting for the processor, maybe a little bit for the memory, and a bit for the graphics card--but then again they're brand new for 4Q2007 and will be top-of-the-line for at least a few months. Also note that you'll be required to modify the graphics cards with a different cooling system to be able to run more then three in "CrossFireX3"(versus modifying two so you can run "CrossFireX4" and shatter most benchmarks).
Processor
Intel Core 2 Extreme QX9650 3.0GHz ($999)
Motherboard
MSI X38 Platinum ($250) (NOTE: normally I don't recommend MSI for boards, but this is the only motherboard that I can find that should support CrossFireX4 at a similar level as an AMD 790FX motherboard)
Memory
2 kits x
Wintex AMPX 4GB (2x2GB) DDR3 1600 SDRAM ($750 each, $1500 total)
Graphics Card
4 x ATI Radeon HD 3870 (RV670XT) 512MB GDDR4 ($270 each, $1080 total)
Power Supply
ePower EP-1000P10-T2 1000W ATX12V / EPS12V Power Supply ($365)
Case
Anything you want--though my preference is as follows
XClio Windtunnel Black ($110)
Hard Drives
2 x
SUPER TALENT FSD32GC25M for RAID 0 configuration (OS) ($850 each)
4 x
Western Digital Caviar GP WD10EACS for RAID 5 configuration (storage) ($260)
Optical Drives
Internal SATA HD DVD Burner
Internal SATA Blu-Ray Burner
Operating System
Windows Vista Ultimate 64-Bit OEM
Accessories
2 x
Kingwin HDP-201 Drive Protectors (to mount the uber-expensive solid-state drives in)
Arctic Cooling MX-2 Thermal Compound
There's some more to add, but as you see that is a VERY expensive computer. I doubt you can afford that.

Tell me when you want to build something and give me a budget.