I finally got some Baltic Birch plywood for my sub project. The lumberyard where I got the plywood didn't have a panel saw, so for a while, transportation was problematic since the 5'x5' sheets won't fit in my car. I eventually managed to borrow a circular saw, so I could cut the wood at the lumberyard to fit in the car.
This stuff is pretty great. It feels extremely sturdy, but isn't ridiculously heavy like similarly sized MDF would be. The only downside is that apparently it won't take stain well. I'll have to play around with some scraps to see what I can do, but finishing is pretty far off, so there's plenty of time.