IMHO, if you bought the birch plywood you should stain it. otherwise why spring for the veneer? Anyhow, I am building my cab from birch veneer plywood. Get a pre-stain conditioner, and I would recommend going with a gel stain. The conditioner ensures the stain goes on evenly, but it prevents the wood from soaking up a lot of stain, so you will need lots of coats if you are going for a dark stain. I am trying to stain mine a walnut shade, and I can't seem to get it dark enough, so I am going to try a gel stain instead.