Thank you very much for your answer! I have a better understanding now
about the new servers. 
Currently ruby enterprise edition is in 1.8.7 and I prefer to use 1.9.2. My problem with the passenger is with the slow initial server response time. I have tried many things (including all the recommendations from here deployment - Slow initial server startup when using Phusion Passenger and Rails - Stack Overflow), but I didn't see any significant difference.
That is basically the main issue with the passenger which I don't know how to fix it and made me thinking of other solutions. If I use nginx instead of apache, will this help with the problem?