You should take a look at Noah car covers if you are interested in a cover that will give you the best all around protection for a decent price. We carry the the Porsche OEM cover as well but as you can see you will pay more for less with that product. Give us a call and ask for me if you want and I can set you up with one. I have the flannel cover for my car because I just use it for indoor storage protection from dust and it is easily washed but I would get the Noah in your case. The covers are taylor made to fit the boxster. Here is the link for the covers....
http://www.tweeks.com/shop?frame=8.1994