I build my own PCs. This is my current primary system:
Case: Corsair 800D
CPU: Intel Core i7 930 Bloomfield @ 3.8GHz
HSF: Corsair H50
MOBO: Gigabyte X58A-UD3R
RAM: Corsair 12GB (6 x 2GB) DDR3 @ 1488MHz
Videocard: ASUS EAH4870X2
PSU: Corsair HX850W
HD: 2xRaptor 150gb Raid 0, 2x Seagate 320gb Raid0, 2xWD Green 1.5TB, 1xWD Green 1TB
Monitor: Westinghouse LVM-37W3SE@1920x1080 (soon to be replaced with a 24" S-IPS monitor).
My secondary system is an i7 930 also at 3.8Ghz, but with 8GB of RAM, and a less powerful Nvidia Graphics card, most everything else but the HDs are the same.
Both systems are running Folding@Home on all 8 cores with idle priority at all times though, so that slows me down a tad sometimes. However the overall systems are easily fast enough to deal with that when running PS on 5dMII RAW images.