You can check two bags in addition to your bike at no extra charge. You can also carry two bags on board and stow them in rack near the entrance to your sitting car. In addition to that you can carry on a very generous amount of airplane type carry-on items to store over and under your seat and if you have a sleeper you can take one suitcase sized items per person into your cabin. And if that is not enough luggage allowance I think some time reading the Ultra-light evangelism thread is in order.
I think some of the East Coast trains are not quite as accommodating.
__________________
On a trip you've got worry as a companion, for you're always concerned about what happens next and sticking to an itinerary. . . . on a journey you never have to worry. Something always happens next.
- Gordon Hempton: One Square inch of Silence