You really can't go wrong with any of the O gauge manufacturers these days. They all make good product.
When you say "traditional sized O", do you mean the same size equipment that Lionel made in the Postwar era, as opposed to the scale sized stuff they now make in their Standard O line?
In planning your layout, it may be helpful to decide what industries will be on your layout before buying freight cars, so that you can concentrate what kind of freight cars would naturally service those industries.
Also, it is a lot of fun to have unit trains to run (all one type of car, like coal hoppers, tank cars, covered hoppers, ore cars, boxcars, refrigerator cars, etc.), so you may want to look at assembling one or two to run.
Andy
