I got a DELL XPS400 customized a bit for around $1600 and am able to push N2K3 as high as it will go and still run around 90+ fps. Which makes losing much more visually satisfying.

General specs with N2k3 in mind

Intel 3.2 DC
800 mb fsb MOBO w/2gb ram
512 mb NVIDIA PCI EXPRESS
SB 3D audio
250gb HD 10k rpm
etc...