RE: effective use of parameters and/or named templates?

This is a site you might find helpful in trying to sort your data by
categories.  You can view their examples and it's source code.  Many of
these examples address the problem you are having.
http://msdn.microsoft.com/xml/samples/index.asp
Especialy this one.  It sorts the different categories.  You can view the
xml page and then change the URL to the xsl page and view it.
http://msdn.microsoft.com/xml/samples/stock-sorter/stock-sorter.xml
http://msdn.microsoft.com/xml/samples/stock-sorter/stock-sorter.xsl


 XSL-List info and archive:  http://www.mulberrytech.com/xsl/xsl-list