It's nice and refreshing to see others recommend John Armstrong's book on track planning. John was a titan in the hobby, right up there with Frank Ellison. I have found the design stage one of the most enjoyable aspects of the entire process, but with that said I would not start with software, that's too much like my job.
As Gregg alluded to, most of us are confined to basements for our dream worlds...shows that women really do run the world I see the plus in this, however, as we can design and build "outside the norm", so what if the wife has to raise the lift bridge to enter the laundry room , she's just going to make you do the wash anyway . Expand the plan in and around the basement, tunnel through walls if necessary...we only live once...and use curved benchwork if you can. When you see the trains running in your mind through the actual space of your basement it'll trigger the next phase and you'll look forward to building.