I used the following and got extremely close sound.
Line 6 Pod Pro
Mesa Coliseum 300 (200 watt per channel tube power amp)
Bellari 562 Sonic Exciter (Like a BBE 482 with a 12ax7 Tube)
Marshall 1960A and B 4x12 cabs replaced with Vintage 30's
Schecter A7 Elite with EMG 707's.
I basically used the Line 6 POD Pro on Insane Mode, no cab emulation, Distortion boost activated, Presence boost off. No effects.
Mesa Coliseum 300 with Deep and Modern Mode Activated, Presense up high.
Bellari Bottom set to about 2 o'clock, Bright Set to 4 o'clock.
Pretty much the sickest tone I ever owned.
Sold the Mesa Amp in fear of having to retube it. It had like 12 6L6 tubes, 6 Rectifier tubes, and I think a few 12ax7's. Basically 2 Triple Rectifier Heads in 1 4 space Rack.
Sold it and got a QSC RMX850.
The QSC was just as loud if not louder but I had to activate the Presense on the POD Pro after selling the Mesa.
It was a loss but close enough to the same tone.
I definately recommend the Bellari 562 Sonic Exciter to anyone looking for a Fear Factory tone.
I always demonstrated to my friends that playing without the Bellari sounded like Machine Head, Activating the Bellari sounded like Fear Factory.