basically, to find a turbo that fits your needs you need to "aim" for the center island of the chart. for example, the turbo you posted would be most efficient when set from 1.5-2.0 pressure ratio (roughly 22-30psi). in that boost range the turbo is going to make 30-45 lb/hr airflow. how much airflow you need will depend on your engine's reqirements.

a rough estimate is 1lb/min=enough to support 10hp. so the turbo above could support (at max efficiency) from ~300hp @22psi up to 450hp @30psi. there are tons of variables to take into account, but this is one of those very rough conversions to help give you an idea.