What D7 settings need changed to take advantage of bigger cloud server I've just upgraded my Rackspace cloud server to 2GB in hopes of speeding up my site. What steps should I now take to enable my Drupal site to utilize this extra memory?

Php mem is to 512MB at present. This is as far as I have gone in changed things (could I go higher, should I?)These are the types of questions I have..
Varnish, Memcache, &amp; APC come to mind. PHP either has enough memory or it doesn't; giving it 512MB wont speed it up.