If you were to get just one item on your list, I would recommend the rotisserie. I have a rotisserie and use it very frequently. Rotisserie cooked chicken is, by far, my families favorite kettle cooked meal. I just store it on my least used kettle.
Troy has loaned me both sizes of the Slow 'N Sear to try out and now, I really want the XL for my 26". If I do end up getting one, it will just permanently stay in that kettle, as it perfect for day to day cooks too.