If you really want to get some speed and lightweight in there..

A setup such as:
apache (latest) run on other port + php 5.3 + xcache (there is more but this is a start) + nginx latest stable running on port 80 as proxy....

Then if your server has more then one core set the process workers for nginx to how many cores you have.. do small optimizations to nginx to cache the images and such..

By the time you know it... you will barely see a load until you really get alot of users..

Also a known trick is DO NOT ENABLE GZIP that is a very bad cpu hog if there is alot of visitors

edit: also you do not need to setup the php intepreter for nginx let apache handle php