I have a Cpanel WHM/Cpanel VPS with Xcache, MPM Worker, latest MySQL, Apache 2, PHP 5 and compiled with Fast CGI enabled. I was wondering if anyone had experience with tweaking a VPS for maximum possible speed and security.

Particularly I'm interested in tweaking the server for maximum possible performance with IPB3, as well as tightening up server security without breaking any scripts in the process..

Maximum performance: get rid of Apache and replace it with nginx.

Personally, I would have gone for memcache over xcache.

You might also try http://blog.mysqltuner.com/ and d/l MySQLTuner