Installer needed for Java based solution

We have a Java based software program that needs an installation package created ? for Windows (XP and Vista), Linux and Mac. ? This installer needs to be Nullsoft (NSIS) or? Installshield based for Windows.? We would like it to be in an MSI package.? For Linux and Mac we would like a Tarball (.tgz format) It should do the usual functions - copying to folder in Program Files, creating icons on desktop, quick launch, and start menu, and have an Uninstaller.? Since this is java based we don't need anything fancy. However, the installer should check for java version 1.6 and if it is not installed, a message box comes up with a link to Java and asks them to install the latest version and run the? installation again.? It would be great if we could download the? java automatically and install it? as part of the installation script. Note: this is a small business project, please bid accordingly.