I know we've had to say this many time before, but I'll say it again: Apache is a hungry beast.
Please, review this article on ars technica as to the difference between Apache and our oft-recommended Nginx:
http://arstechnica.com/business/news/2011/11/a-faster-web-server-ripping-out-apache-for-nginx.ars
Did you know that the entire Arch Linux ARM website runs under Nginx?