There is nothing wrong with 3cx if you cant handle an Asterisk install, Version 10 has just been released and im busy testing it now. 3cx is real easy to configure but with regards to the FXO i have to agree with GMZA, go SIP, it will save you money ! It has been sugested here that you use a Grandstream gateway, they are one off the cheapest out there but i have had issues in the past, in saying that i have not tested the latest firmware and i believe that these issues have been resolved.
1st choice , go VoIP and forget the gateway