I'm using your basic pine from home depot, I would suggest going with a hardwood like oak instead since it will dramatically be stronger and the surface isn't going to dent if you drop something to hard on it. At the time I was scraping to get along with the project so I just went with pine, it'll be fine but it does dent, if I protected the top with epoxy it might hold up better, but i'm not sure if it would be much different compared to the oil based polyurethane that's applied to it.
How I wish I can also do this project. I actually can source a good wood material for the same project for my desktop set-up here but I am planning to hire somebody to do it for me -- an uncle actually who is involved with making furniture am sure he can easily do the job. I am wondering what type of wood are you using here...