Good Z sets available?

In my new Walthers cat for Z it only shows Marklin trains and not very many. Is it safe to say that Marklin is maybe the best and the only one producing good Z stuff. Are there other good Z companies and how do I know its a good product? I would like an old steam loco in my set or should I pick cars and loco separately? Is there a good dependable dealer online for Z Trains? Thanks Ron