Testing J2SE and JEE Applications - Performance - Memory Requirements

My next Java web application is getting ready to go live. Like to have multiple people run tests on this application. So selecting multiple individuals. This application is written with Java, Jsp, Spring framework, MySql and Jdbc. Internally it uses a J2SE library that we have written to convert pdf documents etc. We like to test both for performance, crashing, errors, load handling, memory needed, memory leaks, how many concurrent users etc. You may use SONAR & SELENIUM or any other software of your choice. Let us know what do you plan to use. In the end, we like to know what are minimum needs of our application in terms or memory or heap size or any thing else for different scenarios. That way we can then purchase hosting accordingly. We like to know what all things you can do? Provide us a list. Provide detail and your bid amount / time to complete.