Hello matthew.norman@ers.com,
In my humble opinion, if the the case is Firewall --> Router --> ISP, I would let the Firewall do its duty managing the rules on it. Since Firewalls are there for that purpose, those usually have more advance features to log the allowed/blocked traffic.
Cisco Routers have the 'log' parameter that can be appended to an ACL. However, I would not use that command to monitor all the traffic since it might increase the CPU on the Router. That feature should be used only for troubleshooting purposes.
I hope this helps.
Best Regards.