For finishing pine, I always use Minwax "wood conditioner" first. This is painted on the wood just before staining (follow directions) and it is helpful when staining soft wood such as pine as it helps prevent those random, overly dark blotches that you can get. These happen because of patches of overly open grain in the wood sucking up more stain than the surrounding wood and makes it look like "stained pine" instead of nicely toned wood. I find that I have to use a slightly darker stain to get the tone I want because the conditioner lessens overall absorbtion. As for the hardness of the finish, I prefer oil based poly and I use high gloss for the under coats as it is a little harder. You put the luster of finish you want on the final coat. If you do three coats you should be ok for a while. If you see i dulling out in a few years maybe you could clean, buff and give another dress coat to keep the thickness up, short of sanding etc. With oil based poly don't forget to wear a respirator with activated charcoal to knock down the V.O.C's otherwise you will lose mega brain cells.