This thread really detoured from the OP, but in the last year or so, I've seen a good number of metal bands: Tool, Cannibal Corpse, Whitechapel x2, Shadow of Intent x2, Branded Sacrifice, Revocation, As I Lay Dying, Killswitch x2, Lamb of God, Light the torch, August Burns Red, Acacia Strain, Fit for an Autopsy, Intervals, After the Burial, and Spiritbox. Of all those bands, the only ones I specifically remember having stage amps were Tool, Fit for an autopsy, Acacia Strain, Cannibal Corpse, and Revocation (I think). I believe LOG may have amps running through iso-cabs in the back, but I know they didn't have amps on stage.
In terms of live sound, it's so anecdotal and subjective. In my experience, out of this list, Tool had by far the best sound, which makes sense given their budget and the type of music they play. Fit for an autopsy and Acacia strain (same show/venue) and LOG also had above average live sound. Intervals/After the Burial/Spiritbox, who I saw last week, had just about the worst live sound I've heard in a while. So much of this has to do with the soundman and venue (huge variables), but it just about killed the show for me. I might be overly picky when it comes to live sound, but for me, it HAS to sound halfway good.
After having been to a bunch of metal shows especially over the last five years or so, I've just about come to accept the live sound is going to be mediocre most of the time. It sucks but that seems to be the reality.