When I helped a friend build a pair of 2Pi tower speakers using MDF. We found that veneer to cover front, top & sides would be more expensive than thin solid wood. We glued up for width and used wood glue to apply on to the MDF. I'd done that with my own speakers and it's stood up to the test of time. Also using water based polyurethane used for flooring helps with humidity. And where I live in the summer is very humid. Just an option among many others for you to figure on.