I know a little bit about Rex's rig since I'm a big fan of all his work with Pantera, Down, etc. On Far beyond driven, he used a 4-string black Spector bass (lent by Rachel Bolan from Skid Row), a 5-string Music Man and 2 fretless basses : a Music Man (originally fretted but the company sent to him a fretless neck) and a Fernandes. Considering he doesn't use the low B on "I'm broken", I pretty sure it's the Spector (unlike, for exemple, "Hard Lines, Sunken Cheeks" which should be the Music Man because of the low B). For the amps, I'm pretty sure he used an Ampeg SVT2 w/810 cabs, mixed with either a Sansamp or a little Marshall solid state guitar amp (a white head) for some dirt. After this album, it was the Spector only.
Please someone correct me if I'm wrong but that's what he said in some interviews, his autobiography...
And forgive my bad English !