I've got a 700 too, and I also notice the heat. By the feel of it, the fan blows air out the back. Which means, that it should take in air from the vents near the hard drive. It seems however that most of the air is taken from the ports. So I'm wondering if one of those port protectors might help force the in-take to come from the hard drive vents.
Of course, there must be air coming in from the keyboard, and the cdrom. Though the only place I really feel it is the ports, and maybe it should be that way... just a thought