terima kasih infonya, akan saya pertimbangkan,
Jangan lupa coba nginx, wordpress sendiri sudah pake nginx

http://wiki.nginx.org/Main
"Nginx powers several high-visibility sites, such as WordPress, Hulu, Github, Ohloh, SourceForge and TorrentReactor. "
Cek juga
- pemakaian RAM nya : "free -m"
- Load CPU : "top"
- log error dari apache