You might want to check these guys out, steel not stone. I owned a pizza shop in a previous life and swear by a good stone oven but I've been watching these for a while for home use and really considering it.
http://bakingsteel.com/shop/baking-steel/
I have a couple no names at home and a Pampered Chef one that was a gift. I've had that one to 550 and had no problems but I'm still thinking the steel one is in my future one day.
I have two of the Baking Steels and have never looked back!
Take my advice. . .Stop wasting your money on pizza stones and buy one of these. You can use it for multiple tasks. Making Pizza in the oven or on a grill, baking breads of all kinds, and it can also be used as a griddle. And it will never crack!
Initial cost is made up by not ever having to replace it.
John
A great