Modifying a reservation for a lower price...

I made a reservation online on Sunday 04/16/17 for a roundtrip SEA-EMY in the middle of this September. I was looking at other options for a possible day trip by train during my stay. In doing so, lo and behold, even with the side trip entered into the equation, I came up with a price $200.00 less than my original reservation! The question that I have is do I have to call and talk to agent to get the lower price, or can I modify the reservation online myself? Or even just cancel my original reservation, get an eVoucher, and rebook with the changed itinerary? Any suggestions welcome!

Modifying a reservation requires a call to an Amtrak agent. If the agent you get says there'll be a penalty charge, either ask for a supervisor or call back later to get a different agent.