You may want to give these guys a try. They will take a bit of work, but look good finished. They will also sell you a RTR model for about a $125 (at least I believe that is what the pricing is).
http://unionstationproducts.com/amtrak.html
I am looking for Amtrak California coaches in N-scale. I believe they are Superliner in different livery. Does anyone know where I can find decals in Amtrak California livery?