From PHP -> ROR hosting, hosting customers mailboxes and managing server while migrating to all good Ruby On Rails

Would like to ask some advice from you experts on php -> ror hosting
migration.
Could you guys advice me on this? The memory costs on my regular php
server to run ROR are way to high for me
Think this could be an interesting topic for many php developers who
want to migrate from php to ruby on rails.

CURRENT SITUATION:

# Running a CentOS server with plesk config panel, hosting several
customers all PHP based.
# Customers use PHP based CMS
# I host there mailboxes they each have info@ account with
mailbox.They have no server access, just the CMS access.
# Hosting some personal ROR projects with ruby enterprise on this same
server.

WANTED SITUATION:

# Ruby on rails only hosting, php is no longer needed.
# No more plesk
# Simple way to manage the server ( Add customers and mailboxes )
# Still be able to host mailboxes for customers ( info@)
# End result less mess and things I dont really need ( like plesk)
# End result would be cheaper hosting more value hosting dedicated to
ruby on rails