Nick, I'm not certain what kind of stone Bar Style pizza requires, but, if you've ever been to the NY area, had good NY style pizza and wanted to recreate it at home, without having to go through the hassle of oven tricks/mods, you'll want a better stone than quarry tiles or your average retail offering. 1/2" steel is the reigning champion for creating true pizzeria quality pizzas in a typical home oven. At least it is on the electric side and for gas ovens with broilers in the main compartment. In a gas broiler-below scenario, oven tricks are unavoidable, so materials with lower conductivity will work. Even then, you won't want to go down as far as quarry tile. In that instance, cordierite should be the best bet, with kiln shelves clocking in as the cheapest source.
The nicest thing about a thick, thermally conductive hearth that produces quick bake times is the flexibility it provides. If say, the Bar Style you're working on requires a less than 8 minute bake (quite possible) then quarry tiles won't work. On the other hand, if, for whatever reason, you wish to extend the bake time with steel, you can always turn down the thermostat.