Settings to get the most out of W3 Total Cache

I’ve seen many more complaints about W3TC than WP Super Cache: WordPress › WP Super Cache « WordPress Plugins. W3TC loads the .htaccess file with many directives and tends to conflict with server side settings.

With Super Cache, try PHP caching and follow the instructions to add an .htaccess file to the cache directory: http://wordpress.org/extend/plugins/wp-super-cache/installation/

Disallow /forum caching in WP Super Cache, too.

Minifying js can help with site speed, but not as much as other things, such as server caching and browser caching.

But you also need to work with your dedicated server and correctly configure apache and mysql for high loads. See http://httpd.apache.org/docs/2.0/misc/perf-tuning.html and use mysqltuner to adjust your my.cnf file https://github.com/rackerhacker/MySQLTuner-perl

And clean out your database of post and page revisions (and optimize the database after you do this):

DELETE a,b,c
FROM wp_posts a
LEFT JOIN wp_term_relationships b ON (a.ID = b.object_id)
LEFT JOIN wp_postmeta c ON (a.ID = c.post_id)
WHERE a.post_type="revision"

And then add define ('WP_POST_REVISIONS', 0); to wp-config.php to prevent revisions from being saved again. See http://codex.wordpress.org/Revisions