You should use nginx or litespeed (VERY GOOD website, but it costs money) or lighttpd as Webservers.
This 3 webservers use much lower ressources, so you have more power. Also the configuration of lighttpd is very easy, there is no mpm configuration like at apache.
http://maisonbisson.com/blog/post/12249/chris-lea-on-nginx-and-wordpress/