I'm considering installing Varnish cache in front of my forum platform to speed it up even further.
It already runs Percona MySQL DB, PHP 5.5.8 (which has Opcode caching built in, and running) and memcached. The site runs through a CDN, which also caches some resources.
EDIT: There's no clustering, it's a single server.
Is Varnish a duplication/conflict of any of my current caching layers, or will it be a good addition to my existing caches?