I generally consider a score of 2000 the break off point to play fairly recent games at 30FPS or so at 1024x768 with medium visual quality settings.
That said, 3DMark doesnt tend to reflect overly well with real world gaming performance so I wouldnt rely upon it too much as an example of performance attained in real world games.
Plus 3DMark tends to be significantly better optimized for pixel and vertex shading then most real games,, but tends to be lighter on texture usage, though quite a bit more dependent on various forms of bumpmapping.