Thanks for the replies! Barry, I was originally planning to model "real" locomotives, but am warming to the idea of modeling a miniature railway. It would be just like having your own backyard railway - without all the digging!
Bob, I hadn't thought about the 2-truck locos tracking better than the rigid frame ones. It would also help if you have insulated frogs on your track.
Simon, thanks for the links. I like the loco that Ian Holmes made. That's kind of what I was thinking about. Carl Arendt's layout is nice, too.