I've never used Teamcity, but it looks nice. I do agree chef/puppet can be overkill when you can just do custom AMIs. Definitely make sure you're using proper version control... Honestly, you don't give enough information for a proper opinion, but it'd probably be more informative to just do what you think is best and see how it works out. Ultimately the best workflow is the one that works (even when things go wrong).