Alex,
Just one comment about your multi-level plan; think about what with, or how, you plan to support the upper level, and then think about how that affects what you can see of your trains on the lower level. If you are going to build a table layout, my suggestion would be to keep the lower level on the outside (all the way around) with the upper level fitting in the middle. Conversely (I think??), if your building an around the walls layout, keep your lower level closest to the front and your upper level to the back (nearest the wall) unless you intend to hide what's behind the upper level. Hmmm, maybe not so conversely after all.
Chuck
