Develope Refine Search / Narrow Search for Classifieds Site

I would like to develop a feature similar to the Refine Search in ebay (example: [login to view URL] ) .. it appears on the left side of the page. What needs to happen is, when a user browses a category, the Refine Search should be build dynamically based on the fields applicable to that category and the values in those fields based on listings displayed under the category. Clicking any of the criteria in a particular field (eg. Brand) will filter the result by that criteria. Subsequently, the criteria values for other fields (eg. Carrier) will be updated based on the new list of results. An option should be available to clear any search criteria previously selected. The development should put minimum load on the server. This development is to replace the existing implementation of Refine Search which is too heavy on the server. The classifieds site is developed on 68classifieds script ([login to view URL]) Example of similar features: [login to view URL] [login to view URL] [login to view URL]