When do you need an aftermarket computer?

[Firebat]

I know having a LT1 that goes over 7000RPM is one reason to have an aftermarket computer. What are the other limiting factors to why you would absolutely need one in N/A? I want to build a bigger N/A motor for mostly street use and kind of want to keep it simple by keeping the stock computer. Even though my future build may not have high enough power to absolutely need one but I am wondering at what point you need to start really considering an aftermarket unit.