An extra $2000 or so is what BMW charges you to get a "custom" paint color on your car. I say "custom" because I think they still have some control over the color, and you are of course limited to the colors they have in the factory. You should check with your dealer for details.
Whether you should do it or not is your choice in the end...when I put in my order, I thought about it but couldn't really justify spending that much money just for a standout color. Plus, in your case, I think Topaz is a better blue than Estoril. My personal preference would be for Avus Blue, but that's just me.
