You have a better processor than me [mine's a P4 3.4 GHz], but otherwise our PC's are the same. I get 15-20 FPS with medium-high settings (that means most sliders 3/4 to the right) but autogen on low, and with a resolution of 1280x1024 + 4XAA & 8XAF.
Does it matter? Even without FS one will still upgrade every 4 years or so.
As it has turned out, since FS2000, I've only had two machines. I expect my current machine to last me at least into late 2007, maybe with a new video card, unless other programs I need require me to upgrade.