Christopher,
If you've got the space, don't fall into the trap of the 4x8. It's common, it's popular, it's easy, but it's dated and limiting.
All the kit does is package your purchases in one box. If you go with a "better" (my definition of "better" not necessarily yours) track plan, say from a Model Railroader projects book, you'll still get a shopping list of the track you need, which you can pick up at the LHS or order online.
If you've got a little more room, a modular, or around-the-walls plan like the
HOG will give you broader curves to run larger locos (although you'll be surprised how much space they take up!), and will give you more room for scenery and trains... rather than having everything jammed into 4x8 feet.
If 4x8 is all you've got, and you really like the big power and long trains, maybe you should consider going N-scale.
As far as roadnames - nowadays with leasing, power-sharing and equalization miles, you can see just about any railroad's units anywhere in North America... also, the old saw "It's my railroad, I'll run what I want" applies.