If you think puppet/chef is too much complexity you might find saltstack worth some attention. I haven't used it in real anger yet, but I've really liked what I've seen so far. I see they've even got instructions specific to aws now too [1]
Also worth mentioning cloud formation as well [2]. That might make the pain of chef/puppet more of a worthwhile investment!
[1] https://salt-cloud.readthedocs.org/en/latest/topics/aws.html