Ok, I borrowed from a friend of mine his copy of Doom 3 to make a few tests before reformatting and re-assembling the PC
Demo1 : 640x480 medium detail, no shadows, no specular: 23.5 fps avg.
I also recorded the intro as a demo because this sequence also seems to be very demanding (at least as graphics are concerned):
Intro : 640x480 medium detail, no shadows, no specular 24.3 fps avg.
I'm really impressed. Oh, BTW 3DMark2001 score at default settings is 3940.