I’ll be on the Acela in a couple of weeks, so glad I read this thread. What’s the catering like?
If you go First Class the catering is very good from what I have heard, although I have not experienced it myself.
In "business class" which is what Amtrak calls Acela standard class, you have access to the Acela Cafe which is decent IMHO.
You can check out the menu
here
I should note in Business Class there is no at-seat service, you have to go to the cafe and either consume it there or take it back to your seat.