I don't know if you've played through the game before so I'll put this in spoiler tags.

(SPOILER)There are several endings to CT. Yes, you can go straight to Lavos after getting Epoch, but you have a near-impossible battle ahead of you. Basically you can defeat Lavos at any time now, through different methods of getting to him, but the more you do in the game, i.e. side-quests and finishing the story, generally the better the ending you have.