Just to confirm, but we will be using Post-Crisis versions for most characters. NU52 is allowable if the player requests that version (aside from such updated versions as NU Captain Atom. He's too strong).
Also, generally the tourney will be held in character. The teams are competing to win, but killing and the like is not allowed. So while Superman and Flash are quite deadly, neither is going for the ol' instakill out the gate.