Besides using XSLT...
How to Sort In-Memory XML with Microsoft XMLDOM?
Besides using XSLT...
How to Sort In-Memory XML with Microsoft XMLDOM?
I'm not familiar with any method other than using XSLT to sort XML.
Why is XSLT not an option? It's simple and should not a performance buster. You can cache the FreeThreadedDOMDocument object once it has loaded the XSLT document to avoid parsing and compiling the XSLT document each time.
AFAIK, there is no way to sort in-memory XML without using XSLT to by moving the data to a new (sorted) list. You could copy the nodes to a sorted list, then put the nodes back in the new order. The exact technique depends a bit on your development software.