If you are looking for heavyness, just check out dillinger escape plan on the main stage on sunday-awesome. Speedhorn are quite heavy too (They ruled at the Barfly last night!)
check out amen, they rule on CD and are awesome live. ive seen them for the last 2 years at leeds in the tent but i know they can pull it off on the main stage
Are quite heavy, not in the same vein as Raging Speedhorn or Amen, but they have heavy guitars and are generally awesome. And they're on the Carling stage, which is what you asked for!