There is a sort server behavior in DataAssist that can be used to sort the recordset depending on the selection of a user. The typical scenario for this server behavior is to have columns on the results page that are linkable. When the user clicks on the link the page will be reloaded with the new URL parameter from the link. This parameter will then sort the recordset for you.
Here is a link to the DataAssist support page, in here under Solution Recipes is the Sorting by column links tutorial. There is video and a PDF for it. Please take a look at this doc to get an idea for how to add this server behavior to your results and product listing pages.
Once you are familiar with this server behavior you should be able to use it with a jump menu that has the URL parameters to trigger the sorting. Please post back with any questions that you have about this.