Web filter recommendations request: moderate price with good CGI/PHP proxy filtering



Currently the company I work for currently uses DansGuardian <http://dansguardian.org/> for our web content filtering, but we are having a problem with people using CGI/PHP proxies (such as the ones below) to bypass it. Websense <http://www.websense.com> seems to be the gold standard in content filtering, but the price on it would really hit our budget hard. Does anyone here have something cheaper that I should take a look at?


Here are some of the CGI/PHP proxies we have discovered users utilizing to bypass our content filtering:
<http://56st.com>
<http://www.proxysf.com>
<http://blackip.info>

-aws