This module can filter your K2 content by several extra fields, tags, category and item text at the same time.
--- Display search fields as text field, drop-down select, multi-select, slider, slider with range value select, radio, tag (ability for multiple tags select), category, item title (text and A-Z), item text, item creation/publish dates;
--- Restrict search to specific category (static by category ID(s) and auto by the category you are viewing);
--- Order search fields;
--- Display search fields in several columns;
--- Order search results by extrafields;
--- Display search results in standard category view;
--- AJAX search results.