[take a look at voicegate @ voicegate.com
the ics integrates through a superset
built in call accounting /remote programming w/pc anywhere/built in music on hold
and the best part tech support is excellent
"they never call you stupid "
and they will do custom work also /
1500 + hours/250 mail boxes to start 4 ports and up
4 tenants /voicemail to email capable