For quick searches the drop-down and titles-only view is perfectly suitable. However the “show more” button should actually show more in a wider sense than just additional search results.
This does not:
How about making the “show more” button take the user to a new page, showing search results with excerpts, similar to a user’s activity stream? I know discourse is all about not leaving the page, but I think once a user wants more than the top5 search results, they’re in full on “search mode” - it’s not just a quick sidestep any longer at that point.