If it were me, I would take VIA Rail's "Canadian" from Toronto to Vancouver instead. Getting to Toronto from Pittsburgh via Amtrak would involve an overnight in New York City, so I would just fly to Toronto instead.
The Canadian leaves Toronto at 10:00 PM on Tuesdays, Thursdays and Saturdays so if you catch a morning flight you would be fine. The "Canadian" while quite expensive is more luxuries than anything Amtrak can muster. Sleeping car passengers get their own lounge car separate from coach passengers. The dining car is superb and sleeping car accommodations are top notch (you would probably want to get a double bedroom). Once you get to Vancouver you could spend a few days there and take the Amtrak Cascades to Seattle, do whatever sight seeing you desire and fly home from there.
Anyway thats just what I would do.
http://www.viarail.c...couver-canadian