I more prefer w3 total cache rather than wp super cache.
It has more options, and many things to tweak, but its harder to setup.
- caching
- gzipping
- minifing
- object cache
- browser cache
- etc
@ DVTimes, try cleaning and optimizing DB also
Also, make CSS sprites.
..
..
at last: configure CDN for static components
and if you need more computing power, make it on two dedicated servers
