IP Address Management IPAM software for small ISP

I'm looking for IPAM solutions for a small regional wireless ISP. There are 4 Tier 2 personnel and 2 NOC technicians who would be using the tool, and a small staff of engineers. They have regionalized IP addresses so blocks are local, but there are subnets that are global. don't care if it's a linux or windows solution. Need to be able to migrate from FreeIPdb (yes, I know, it's a dinosaur) We're not dealing with a lot now, but the potential for growth is pretty high. What are you using and how is it working for you? Much appreciated, Eric