I believe I am as confused as you are after reading this question. I'll provide some information to you and hopefully this clears things up for you.
Adobe LiveCycle ES is a server side product that allows you to ( in addition to a few hundred other things) merge XML data with with a PDF template created in Adobe LiveCycle Designer. You don't need any other framework to merge any sort of data with a PDF template other than LiveCycle.
Adobe XI Pro is essentially Adobe Acrobat (desktop product) that allows you to perform a number of operations in the desktop environment. It will not allow you to merge data with XML on the fly since this is something that the server side products do.
Hopefully, this information clears things up for you. You would need to talk to Adobe or one of its partners to get a license for Adobe LiveCycle ES before you can use the product.
Please let me know if you have any other questions.