To be NIMS compliant, all front-line first responders are required to have ICS-100 and NIMS-700. 200 is required if you will be in command of a single resource (which covers most EMTs, who will be in 'command' of their ambulance). First-line supervisors are required to have ICS-300, and Chief Officers require ICS-400. I don't know where 800 comes in, though I have it and found it to be an enormous waste of my time.
Incidentally, ICS-300 is 24 hours of death by powerpoint, and I would rather have a root canal than sit through it again. That was one of the (several) times I have questioned my sanity for becoming an EMS officer.
If nothing else, you learn interesting things. For example, don't request a 'tanker' for a fire while out west, or a large plane will fly overhead and soak you in red stuff. Also, if you ask for 'six buses' for your MCI patients, don't be shocked when school buses pull up, since you should be asking for an ambulance if that's what you need.