If you don't need 3d, Matrox makes nice cards with great 2d image quality. I've seen some in our engineering dept that have 4hds on them. G450's or G500's I think they are.
Matrox, has a gizmo, that splits up the signal to 3 monitors at a time, check it out. Maybe if you have a dual head card, you could use two of them, not sure though, but worth looking in to ? If his setup allows the use of the onboard (if equipped) graphics also, like ATI's 200 chipset, maybe that would get him there. Just a few thoughts.
Yeah, nearly everyone on here will recommend Matrox. They make fantastic products for quality 2D rendering.... I can remember having a Millennium WAYYY back in the day, and it was fantastic on my 19" CRT. *SIGH* I also had a Black Magic 3D.... I was a bit of a nub back then and didn't realize that the Millennium I had actually had BETTER 3D quality built on the chip than the dongle-attached 3D card. I still have those cards sitting "somewhere" in a PC....
you can always get a few pci vid cards with dual heads i have extra pci cards in a few pcs to run extra monitors on not sure if there is any draw back to my technique but works fine for me