Whygee, I've never seen an electric oven with a dial that didn't either go to 500 or 550- at least, not here in the states. In Europe, you frequently see ovens that go below that, which are abysmal for pizza.
Some ovens with dials that go to 550, especially older ones, can reach 600 actual temps, but you'll also find the occasional oven that undershoots it's target temp. I know of no currently available models that can guarantee that they'll run on the high side.
I think you can hedge your bets a bit by going with a 550 dial oven, with the ability to go 35+ degrees via calibration. I don't have a model in mind, but I think calibration is popular with most high end ovens.
Wattage will give you a pretty good idea of what it can do, but a look inside the oven, at the actual coils, will go a long way as well. Neapolitan wattage is pretty much impossible to find, but a broiler with plenty of passes will go a long way for NY style bakes, and could encroach on Neapolitan. You can't have too many broiler watts.
Here is the Rolls Royce of electric broilers:http://www.pizzamaking.com/forum/index.php/topic,16227.msg167250.html#msg167250
To be honest, while doing your homework before shopping for an oven is the right way to go, we haven't had a whole lot of these types of conversations on this forum. While just about any 550 dial temp oven should serve you well (plus perhaps a convection feature that allows convection at 550), if you can post any details of models you're looking at here, it will go a long way in helping us help you narrow down the field to the worthiest of candidates. If you can post photos of the broiler element, that would be useful too.