You're quite welcome. My son loves trains, too, and I also got something out of it. I wound up buying that big 1000-piece one, the side view of the train-yard-- he's never tried a 1000-piece before, but that one seems to have a series of well-defined small areas that are like small self-contained puzzles. I am trying to teach him that he has no boundaries, so I plan to have him work on this, even if it takes a while, and I know his train mania will keep him at it.

I think some of those kits look really neat, too.
I know what you mean about the floor puzzles on carpet. He generally has commandeered a section of the kitchen when he has worked on those.