I think you'll be needing a combination of both IP Address Manager and Network Configuration Manager for this. IPAM only deals with maintaining the list of addresses you have available, not actively divvying them out. That'd be done by your Cisco DHCP or equivalent. In this example you would add your Cisco DHCP as a DHCP to IPAM, and then configure the superscopes/addresses from within IPAM. The DHCP server(s) would then start dishing out the addresses, and you can use the historical information to search which device had which IP using it's MAC/BIA, among other things.
Network Configuration Manager would help you configure your end devices, as it supports the automation of deployment of new configs and the running of scripts against devices it manages. Using this product you could connect to devices once deployed and make any changes remotely.
With both of these products working together you could manage both your modems and your IP addresses from one product
Hope that helps!