To keep things simple, I would just use the following 5 subnets:
192.168.200.1 - Switch (no VLAN needed)
192.168.201.1 - Modem #1 (VLAN 201)
192.168.202.1 - Modem #2 (VLAN 202)
192.168.203.1 - Modem #3 (VLAN 203)
192.168.204.1 - Modem #4 (VLAN 204)
That way you keep everything away from the common default IPs, which may cause you problems in the future.