Like the others said, Wordpress can handle this amount of traffic just fine.
I would suggest one of the two caching plugins. These plugins write database-heavy pages to disk, which saves load on the database server. The difference is remarkable.
WP Super Cache
W3 Total Cache
Both are well-maintained, the latter has more features, but can be intimidating.
If caching doesn't seem to help much, your problem might be in different areas. Web server configuration can be tweaked (adding gzip compression, adding Expires headers) and even theme HTML has an impact (seek to minimize the amount of requests your page is doing). I would need detailed information to help you out.