Modules needed to create the best WYSIWYG experience?
You will need the Drupal WYSIWYG module http://drupal.org/project/wysiwyg and the TinyMCE Library here http://www.tinymce.com/

TinyMCE supports plugins and you can make that "best WYSIWYG experience" that you are looking for. You can hook it up with your theme CSS and apply styles to the text aeras and see them in the WYSIWYG. Also check the WYSIWYG plugins page http://drupal.org/node/1197256