I thinks it is better if you use the accounting funtion on each your Cisco Gateway, not in the GK. Because the Cisco Gateway have built-in this funtion in the IOS and this is work right, so no need to use the accounting funtion in the GKs, since the GKs will work better.
About the Telecount Billing or Mind CTI Biiling system for prepaid calling card. The Telecount is cheaper than but this could give you the same funtion as Mind CTI. I don’t think the Telecount do not support right for Cisco equipments, because all of the Prepaid Billing system as Telecount or Mind is based on RADIUS protocol to built their billing, so I thinks the Telecount will work right with all of the equipment which is following the RADIUS protocol.