Kev Bower from HELL here - just thought I'd throw in my opinions which may help.
One of the main reasons why our album sounds the way it does is that we used exactly the same gear as we did in in 1985 - my Hamer Explorer with passive Seymour Duncan pickups (SH5 Custom bridge, plus the SH1 '59 on the neck, straight through a Marshall JCM800 50-watt head (they distort better than the 100-watters) into a really old Marshall 4 x 12" cab with ancient paper-coned 30-watt Celestions.
The only FX used in the signal path were an Ibanez TS9 Tubescreamer with everything set to 12 o'clock, plus an old Boss NF1 Noise gate to clamp everything down. That's all. It sounded fuckin' amazing.
I've worked closely with Andy Sneap on this album obviously, and the guitar sound is way different from his standard go-to setups for more contemporary-sounding metal bands - usually a 5150 or Randall head with a Mesa 4 x 12" cab, but in all cases the recording is the same, made with an SM57 pointing straight at the speaker cone, plus maybe an additional mic (a U87 or similar) placed a few feet away to pick up some additional air movement. The key differences between old tube amps and their newer counterparts are that the new stuff a) has more gain and b) usually has tone-shaping built into the circuits to suck out mids etc.
The key thing to show out here (and this is my point at last!!) is that the character of the sound comes from the combination of the guitar, the pickups, the amp and the cab - not from any fancy gadget you place in between, which IMHO only usually serves to completely fuck the tone. The Tubescreamer is probably the only pedal which adds gain and a little compression without screwing your tone - hence why they've sold millions of them. The only other stompbox I've ever heard which is anywhere near as good is the Blackstar valve one. My advice is to forget distortion pedals and save your money for a better amp. Not easy I know, but it's 100% the way to go, especially if you go secondhand. Try the Marshall DSL 50 - it's KILLER for the money.
Best wishes to all