Xeon E5645 @ 3.1GHz(1.1V), Asus P6X58-E WS, 6x4GB Kingston ECC DDR3@1333
eVGA GTX570, Antec P183 with CP-850 PSU ...and still whisper quiet.
Old faithful:
Opteron 170 @ 2.5Ghz(1.425V), Asus A8N32-SLI (bios 1205). Corsair TwinX2048-3500LL (2x1024) @ 250MHz (2.5-3-3-7 @ 1T, 2.7V)
eVGA 7900GTX, HDA X-Plosion Seasonic S12-500 with SStn PP01 ATX cable extensions.
Antec P180, VGA duct removed. ...oh, and lots of *SILENCE*