Trying to out-specify problematic upstream Drupal 6 styles at the theme level is a nightmare. Instead we will just replace them with SASS _partials.
For example, to override "/modules/system/system.css"
- Add a stub to theme.info to prevent loading. Note: The path doesn't matter, as long as the file name matches the default stylesheet won't load. Don't forget to clear your cache.
stylesheets[all][] = kill/system.css