Mid 600s from a 75mm primary and 5x16s isn't that bad. Good tuning will get you a little higher. But if you want big numbers, you need bigger injectors and a bigger primary.
I don't have any experience with your particular charger set up, but I do know for a fact as long as you have a stall of atleast 2000 or higher you will like the 72 more, I know we did going to s472 from s300g over ht60
When you're going big as to what y'all are speaking, which produces better...compounds or singles? Obviously there is more to it than just turbos or injectors, but don't compounds light quicker than a big single, w say, same inj???