I really haven't heard it live (only on records) but for various reviews and some GT forum questions, I learned that what you are looking for (considering the type of sound you want and the kind of money you will put on a 5150 amp) that the right amp for you is the KRANKSTEIN.

Celestion equiped, designed by the allmighty Dimebag Darrell, seem like the flawless metal amp ever made.

Christian Olden (fear factory) said that you won't need any stompbox or pedal to have this monster ripping thru anything, wicked distortion that catches the escense of its maker trademark sound, lots of bottom end evil midranged for those high pitch squealz or pinth harmonics (gosh I think I started to get goosebumps) and bout the clean channel, I've heard is crystal clear, shiny and very nice sounding too.

You can hear a sound clip on the net (not very reliable but it may work for you) at the krank webpage ( think it's krankamps.com), or check Fear factory last realese TRANSGRESSION, but the best would be if you could take it to a test drive at some store.

If you get it (damn I hate you) I'm sure you'll be VERY pleased with it, cause it sounds just like what you are looking for.