We recently invested in some new workstations for our office. After doing some research, the following specification was settled on:
Intel Core i7-975 Extreme Edition Processor, 3.33 GHz
12GB (6 X2GB) Corsair DDR3 (1600MHZ) 9,9,9,24 Matched Triple Kit, 1.65V, TR3X6G1600C9
Quadro FX-580, PCI-E 2.0, OEM, 512Mb, GDDR3, 128-Bit
WD Caviar Black 1000GB / 1TB SATA-II, 7200RPM, 32Mb
Genuine Microsoft Windows VISTA BUSINESS 64-Bit DVD OEM SP1
I am also running dual monitors, one being a Samsung 740B 17 inch monitor, and the other a beautiful Samsung 2443BW 24 inch HD monitor.
And Revit loves it!