Chris (Club Neon) walked me through my first full computer build. Many long work days later, it keeps ripping without a flaw. (Just knocked on wood!) It screams, is stable, and runs semi-intense CAD/CAM/FEA 2d/3d without a hickup.

Vital Stats:
SuperMicro Barebone Tower/4U S-1366 for i7 CPUs (Good layout, but short wires on optical drive section.)
Radeon HD 4870x2 2GB GDDR5 (Screams, but make sure you have enough power for it.)
Intel 920 i7 CPU (Great chip, check Tom's Hardware to see it keeps up with many of the overclocked models in real world tests.)
12 GB RAM (4x4x4) (Keep the tripple memory path in mind when budgeting - can't do 8 easily.)
Vista Ultimate 64-bit
4 TB Seagate Cuda Drives (Raid 1 x 2) [Suitably fast and big so far - and cheap now!)
2 23" Samsung LCDs (Too damn wide, but good for most applics.)
850 Watt Power supply (Lacked on 8 pin needed for the beast from Radeon! Made for a pain in the arse.)
Pioneer Blu-Ray burner (Plays BR movies smoth, and burns disks fast.)
Wacom Intuos4 graphics tablet (Cool!)
6 or 7 cooling fans (better have a good A/C path as the heat from this beast is a factor in a small office.)
Oh, and a Lexmark X9575 Wireless MFP - which kinda sucks for the price.

Panny 3000 PJ, 118" Carada, Denon 3300, PS3, Axiom QS8, PSB 5T, B&W sub, levitating speaker wire