Definitely look for IRs, they are a must. I bought the redwirez stuff and don't regret it one bit.
For my high gain stuff:
-Two cabs: one 0in cone the other 1in cone
-Two amps: one for the actual tone/feeling, the other for the low end (tweak each accordingly). Pan each amp just a little (I do balance around 20/-20)
-Separate signal chains for the two cabs/amps after a gate
-Give both signal chains a boost (I typically use the OD808 gain on 0, tone around 3, level at 9/10)
-Just a little reverb (seriously, just a little). I do medium plate, 1.5 sec, 50% mix, -5db level,
-I like the "enhancer" at the very end of the signal chain (right after the reverb) at 85% or so
-Cab blocks: room size at around 5, play a little with the mic spacing, change the low cut frequency (I like it around 20 Hz), play with the "air" setting, I usually like it around 20%.