Some people use a stain with clearcoat and many use various finishes of black. Some even use bedliner textured black. I'm starting a plywood pair of boxes next week and it will probably go black with a clear finish but I'm not going for piano glossy black lacquer. I have considered using a fomica type laminate because it is so durable and relatively easy to apply. My room thus far is all utilitarian and I want the speakers to disappear so black is my choice.
Sr7009 + external amp for 9.3.4
jbl - northridge x11; sp6cii ceiling
Dayton HF15 sealed x2 on xls1500
av123 mfw15 w/ bash 300