Hello Charlie:
I’m a CPM GW’s owner, and can tell you it’s the most complete solution for your needs. It includes billing, prepaid and postpaid modules for customers and ITSP’s, IVR (with up to 10 languages you can customize easyly), PC to Phone, Cisco compatibility, and so; everything included with the software supplied by CPM.
For Cisco and Quintum, you only have the voice gateway, and have to add other hardware and software for billing, ivr and the other features.
Depending on the number of ports, the time to setup and other circumstances, you can find which brand and solution is best for you.
Muchos saludos,
Edwin