The two best live metal tones I've heard were Iommi in '07 with Heaven and Hell and Cannibal Corpse (basically the same awesome tone every time I've seen them). My personal dream tone is a more hot rodded British sound. The modded tones from Monomyth, Gower and Eric from Omega are all of interest to me plus the new Dover DA50.
TLDR: upper mid range keraang, articulate, tight and that Marshall bassy sag.