I think what you really want is a CDN of some sort. That will take load off your server, and serve static content for you from a global network. Browsers are configured by default to cache content. As long as you use good expire headers on files you should be okay. (you may want to compile in mod_headers and mod_expire into apache if you do want control over this.
you may also make sure compression is enabled for browsers that support compression so that the size of the site data is much smaller with gzip compression. I don't remember if this on by default or not in cpanel.. (you can install mod_deflate) for this.
I usually use rules like this in htaccess, although you can customize them for how you want.
Code:
# 1 YEAR
ExpiresActive On
<FilesMatch "\.(otf|ico|pdf|flv)$">
Header set Cache-Control "max-age=29030400, public"
ExpiresDefault "access plus 1 years"
Header unset Last-Modified
Header unset ETag
SetOutputFilter DEFLATE
</FilesMatch>
# 1 MONTHS
<FilesMatch "\.(jpg|jpeg|png|gif|swf)$">
Header set Cache-Control "max-age=2419200, public"
ExpiresDefault "access plus 1 month"
SetOutputFilter DEFLATE
</FilesMatch>
<FilesMatch "\.(xml|txt|css|js)$">
Header set Cache-Control "max-age=604800, public"
ExpiresDefault "access plus 1 week"
SetOutputFilter DEFLATE
</FilesMatch>
# 30 MIN
<FilesMatch "\.(html|htm|php)$">
SetOutputFilter DEFLATE
</FilesMatch>