Gosh, just when this is getting really interesting, my son wants the computer to play "Oregon Trail"! I hope I'll be able to get back to this discussion later ... thanks for your patience, and although I picked nits on your article, I think the general approach you and your collaborator are taking is outstanding!
Christmas is coming, and computergeeks.com has a ton of refurbished computers for under 500 dollars, some of them quite up to date.