CPU Usage getting too high. Already have Wp-cache, High traffic, What to do?

My dedicated is on a Quad Core Intel Xeon 3210, 4GB memory. ~25k uniques a day, and my cpu usage hits as high as 95% at times. What can I do to reduce the cpu usage? Query cache is already enabled with a large amount of memory dedicated to it. I saw a post about Eaccelerator php acceleration, but Would that work with Wp-cache? Please, Any info would really help. What could I Do to reduce cpu usage? I Do not have a lot of plugins, I only use Wp-cache/Seo plugin/Wp-ratings/ Thats it!