I did not railize that one can upgrade on an Amtrak train, but it is railly possible. I am not line to you or trying to railroad you.
Hitching up to the On Train Upgrades? thread will get you on the right track on how to do so and what the chances are of upgrading on board a train with a coach ticket. Other FlyerTalk members are using their engine-uity to break the tie of how to successfully upgrade on a coach ticket for TrainTalk – er…I mean FlyerTalk – member Train McGhee from Chicago to Seattle who hopefully will not get steamed by the answers.