[OpenSIPS-Users] Choice strategy

[pavel@eremina.net]

Opensips such SIP Proxy i use more than year and it's good enough.
But now i want to add Asterisk for add Hosted-PBX service for our
clients. In general i know that Opensips can route trafic between
sip-users and when users want some media service like voicemail, hold,
anounce. ivr, parking and other else, Opensips will route there
request to Asterisk.

Two question:
Is this scheme good for all voip services (fax, conference, inbound
call distribution) nor not?
Can i use SEMS instead Asterisk for all common services?