This post is a handy guide -> http://www.showthemes.com/blog/choosing-event-wordpress-themes/
Selecting a WordPress theme may seem like an easy task and saving a few bucks may expose you to a bunch of other problems.
Said that Showthemes is not the only legitimate theme author and provider out there. There are a bunch of others doing original work and properly supporting their themes.
We pride ourselves of having become the leasing independent provider for event WordPress themes and this is thanks to our clients and their feedback!