Not sure about the actual stone temp but I do a 550 preheat for 30mins. Are you baking 6 mins to darken your crust more or melt the cheese? I found by increasing the oil it helps with darkening the crust more.
My oven goes only up to 500, which means I can get my stone to about 530 on the bottom rack, if i repeatedly open the door during an hour long preheat. I throw the broiler on during the bake for top heat, but have considered an arrangement like you have, with tiles above.
Ultimately, I am not worried about colour. I want the bottom crisper, and a bit more oven spring would allow me to stretch thin without the slices getting soggy...