Bandwith Management and access control

Hello,
We are planning to become an ISP. We would like to have feedback on the following solution.
we have to distribute bandwidth to different clients. We have got cisco 1800 where actual link would be terminating. further it would be distributed from switch connected to cisco 1800. What would be best 1) to connect a managable switch or 2)to connect a firwall; for bandwidth management and utilization.

Also suggest what would be the best for bandwidth management.
Thanks,
Kunal K.