I second Media Monkey. I've used it for years to Manage my 4K+ library of music. it has a simple interface and tools that allow you to easily edit mp3 attributes, tags, and add album art to files. When i went trough my collection it was a lifesaver.
Now, since I've gotten Google Play Music i uploaded my library to that service, and just use it to play my music. My i get both music from their service and my own library.