In general, DC's need to be met, not exceeded, to succeed. So if the Spell DC is 13, after bonuses the creature making the saving throw needs at least 13.
Originally Posted by Grod_The_Giant
We should try to make that a thing; I think it might help civility. Hey, GitP, let's try to make this a thing: when you're arguing optimization strategies, RAW-logic, and similar such things that you'd never actually use in a game, tag your post [THEORETICAL] and/or use green text