Well Regional and Acela are the only way you can do that. As for which one takes less time, obviously Acela is the winner, but it also comes with a price. Regionals only take about half an hour longer if I'm not mistaken, and for the ordinary traveler suit their needs just fine. Regionals come in two forms, reserved and unreserved. Unreserved trains are cheaper to travel on, but there is no guarantee that you will have a seat (although the odds of not having a seat are pretty slim). Unreserved trains also allow flexibility in that you can travel at your leisure between the hours that your fare allows. Reserved trains guarantee you a seat, but you also must board that train and only that train on that day. As far as equipment differences between Reserved and Unreserved trains there really is no difference, they both pull from the same pool of equipment.