For my two dual subs I went to a local granite yard. Found a couple matching color sink cutouts as remnant and had them cut to 14x16” and flat polish them. Those are glued to the tops. For the bottoms had them cut some matching remnant 16x18” so it has a 1” lip at the bottom. Cost was dirt cheap compared to a professional painter and it makes the cabinet rock solid. Pun intended. Downfall is that it adds 80lbs. For the sides I am waiting on a local wood working guy to kiln, mill, and cut and sand and finish 4 (exotic) panel cuts of wood to glue on. The wood came from my back yard when I recently cut a maple tree down.