I don't think that's true - I have a machine with 4 GB RAM & a 2.x Core 2 Quad. I have no memory problems, but I do have lag when using KDE or GNOME that's not

I don't think that's true - I have a machine with 4 GB RAM & a 2.x Core 2 Quad. I have no memory problems, but I do have lag when using KDE or GNOME that's not present with Openbox. I haven't tried Xfce so I can't comment on it, but I'm guessing it's at least a little better than KDE/GNOME.