>> I find it not easy to compute the capability of jboss eap
True, you cannot compute it simply based on hardware configuration.
There is a huge performance difference if you compare 1) hosting only some simple static html pages on JBoss ; with 2) a complicated Java EE system which depends on different technologies (such as EJB, JMS, Webservices etc.) and when there are also some other limits on other resources such as databases or backend services ...
Can you give me some rough scale, just like 10,100,1000, ... for the situations that you said above.