That's a nice looking chunk of steel there, Chaz
I can't tell from the shot in the oven, but did you take the mill scale (dark colored coating) off? It's not essential that you do, I'm just curious what your cleaning regime was.
The temperature you should be shooting for is whatever temp you need
Seriously, though, there are a variety of factors involved, hydration of the dough, fermentation time, added sugar/residual sugar, oil, thickness factor, desired style- these all impact the temperature you'll need to bake the pizza at.
The good news is that 574 will give you any non Neapolitan bake time you could possibly want. With 1/2" steel, 574 might even break the 2 minute Neapolitan barrier- on the undercrust, of course. The top would most likely require a stronger broiler than you currently have (it wouldn't hurt to check, though), making the Neapolitan undercrust capability moot.
Generally speaking, for NY style, you're going to want to be in the 500-525 realm. If you're going with the last formula you used:http://www.pizzamaking.com/forum/index.php/topic,22834.msg231958.html#msg231958
I would try 500 first, then 525.