GitHub User: cmer
I recently released a very simple alternative to Chef if anyone's interested: https://github.com/cmer/shoestrap
Here's what you're looking for: https://github.com/cmer/shoestrap-example/blob/master/helpers/default#L162
Unicorn is significantly faster than Passenger. A well-tuned MySQL install performs similarly to a well-tuned Postgres install.
Nginx is generally much simpler to setup than Apache. It's also faster and less resource hungry.