i'm running huge programs like AutoCAD 2009, World of Warcraft, crysis, and tons of other home designing programs.
Have a look at workstation layout at My dream computer, though I'd wait a bit for dual-processor system (seem to come out in 2-3 months). The chipset will be the same (or nearly the same). You would not need more than 8 cores (really most Windows software cannot use even two).
Two-core system will also allow bigger (ECC!) memory per processor and will allow creating ram-drive (quite helpful for ACAD) - 4GB DDR3 ECC already exist.