I wouldn't think of using anything but poly. Otherwise the floor will start to wear and the dirt will get ground right in, not pretty. If you are going to stain first, use minwax wood conditioner and adjust your stain darker b/c it will be about half as dark after the conditioner. You can use a scrap for testing. Also, if you are staining be sure to stain the edges and/or the tounges so that if it shrinks and gaps it will be dark and not light. Also, let the wood aclimate for at least two weeks inside your house before installing it. It must be stacked with little pieces between each layer to allow air in there. If the wood is a different humidity than your house you are more likely to end up with gaps or ridges. I think it is better to install it in the winter when it is dry and shrunken. If installed in the high humidity of summer it is more likely to end up with large gaps later on. Of course this means that you need at least 1/2" gap left all the way around between the floor boards and the walls or baseboards, otherwise if your floor swells it will buckle or push your walls out.