If a huge chunk of your database is split between 20 evangelists, and you know that the evangelist program is going to be a long-term initiative, you could create fields on the lead records. They'd be similar to the Lead Owner fields, where you have to update the lead information and you can use tokens to display the correct evangelist per territory.
You could also use Segmentation for this too; group leads by territory and place them in different segmentations so you can use signature snippets in your emails. Then you'd only update one email instead of 20 🙂