You need some G12Hs or clones there of (Warehouse Reapers, or Reaper high powers maybe) and a good fuzz or fuzzy sounding amp. You can always use a bit of the fuzz, and a bit of the amp too. A recto on Raw with a fuzz up front sound awesome. I do so with a Russian Big Muff, but I'm looking into picking up a Death By Audio Fuzz War, Devi Ever Hyperion, Super Massive Black Hole, or a Blackout Effectors Musket Fuzz. The recto on its own can get pretty nasty sounding too.
You got any samples of your setup? I wasn't going to touch Mesa because in my mind they were always the champions of super tight/clean metal rather than crackling fuzz and bass.
I know the chances of you seeking and actually picking up an Electric Amp head are minimal at best but I'm going to just post a couple links to clips of them just so you can get an idea. They have tonnns of low-end. When I recorded video of mine, it was hard to keep the camera still because the amp's low-end was vibrating it all over the place even at modest volumes. Very raw and buzzsaw sounding distortion, vintage voiced, and aggressive as heck sounding.
Not up everyone's alley. I just happen to really like them. They're very sensitive to what pickups your guitar has as well so their sound can vary. You may also want to look for a Matamp GTL or GT1. The GT1 is pretty affordable if you order it direct from their factory.
EDIT: Tip, the sound on Electric Wizard's "Dopethrone" album is just a Boss FZ-2 into any loud amp. I have one here and it's simply 100% identical sounding to that album so if you want to cop that tone, just camp out on Ebay looking for one.
Hiwatt is watt (harhar) I've got my eye on at the moment, a Hiwatt Hi-gain 100 head maybe? I don't have any experience with Hiwatts, so if you have any suggestions go for it.
Jus from Electric Wizard's mainstay in his rig has almost always been a Boss FZ-2 Hyper Fuzz. He pretty much plug that thing into whatever head he can fine (Which right now is some late '60's Hiwatts). The reason for this being that he didn't own a head for a long time, and he just borrowed from friends or rented.
You can really hear the FZ-2 on the Dopethrone and Come My Fanatics albums. What he's using on there is the FZ-2's 2nd mode, which is just a relentless buzzsaw fuzz.I love it.