There are multipl things.
1.) First of all you need to make sure your site is running without any errors in the apache log. Components and plugins that create a lot of errors will slow down the site significantely
2.) Make sure sh404SEF cache is enabled. Check how many URLs are in the cache.
3.) Upgrade to 1.0.5 if you have not done so. Its faster and creates up to 10x less URLs which in return will help sh404SEF keep up the performance
4.) Minimize the amount of plugins and mambots. Every addition requires extra resources.
5.) Consider running on a dedicated server. 8000 unique visitors per day is some very decent traffic. That should put you well above 2M pageviews per month.
6.) Make sure your MySQL database is configured correctly and is setup with the proper amounts of caching memory.
7.) Make sure you have Joomla caching turned on for as many modules and plugins as possible.
8.) There is a great caching product available for Joomla. It is not free but cheap and the results are amazing. It is called Cache Accelerate Component for Joomla. See link below.
It chaches all pages for non logged in visitors and you can set the frequency how often the cache should get refreshed. I use it on my site with the cache TTL set to 3600s (1h). It has brought down the page load times per google webmaster tools from an average of 2s to about 300ms average. Individual page loads will vary based on connection. It aslo covers the RSS feeds and takes a lot of visitor generated load off your server. People that log in still get to see every page in real time. If you can afford a 1h delay (or more) for bots and visitors this is the way to go.
extensions.joomla.org/component/option,c...k_id,1341/Itemid,35/
Hope this helps!
