Choosing the right litter box

Question
I have an 11 pound Ragamuffin who tends to fling litter all around her box, and it's a mess to clean up.  I've been thinking of a box with a dome top.  There's one that sifts out the messy stuff when you put it on its side.  Do you know anything about this?  Might it be a problem to get a 5 year old cat to climb into a box like this?  Any thoughts you have would be appreciated as I'm a novice cat Mom.

Thanks
 Dana

Answer
just buy whatever type of covered/hooded box you want and dump her dirty litter, poops, pee and everything into the new box and dont clean the new box until she has used it at least once. its just that easy. oh and be sure to put the new box where the old box was so she will go to it naturally