I have an under spec machine -
AMD 3200+ single core @2Ghz an ATI 1950pro (512 AGP) and 2 gig of ddr and the game runs fine.
All graphics settings are on high except for shadows which I turn off and grass I have on low, unit size is on Large.
The only performance issues I have is the sound on the intro movies stutters and the map is a bit laggy every now then but nothing like ETW.
Hope that's of some help
LDC