For our amp and mixer, we use an 8 space SKB.
For my 2 sound modules, I use a RokSak. This way, if a place has in house sound, I just bring that. Otherwise, the whole rig.
As for plywood - Well, plastic was invented for a reason. The reason is waterproofing. Plywood absorbs smells and spilled alcoholic beverages with an unreasonable thirst. This leads to mold and weakened wood that gets soft and yucky.
Not that I would know by having had pints of beer spilled on mine and having to replace it three times in four freakin years...